chore: update issue, pull request templates and contributing guide

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -6,6 +6,10 @@ body:
     attributes:
       value: |
         Thanks for taking the time to fill out this bug report!
+
+        - For questions, ask in [Discussions](https://github.com/flamego/flamego/discussions).
+        - Before you file an issue read the [Contributing guide](https://github.com/flamego/flamego/blob/main/.github/contributing.md).
+        - Check to make sure someone hasn't already opened a similar [issue](https://github.com/flamego/flamego/issues).
   - type: dropdown
     attributes:
       label: Component
@@ -18,7 +22,7 @@ body:
   - type: input
     attributes:
       label: Middleware
-      description: If this is for middleware, please specify the repository URL, e.g. "https://github.com/flamego/template".
+      description: If this is for middleware, please specify the repository URL, e.g. "https://github.com/flamego/template". Otherwise, put "n/a".
       value: "https://github.com/flamego/"
     validations:
       required: false

.github/ISSUE_TEMPLATE/documentation.yml

@@ -6,6 +6,10 @@ body:
     attributes:
       value: |
         Thanks for taking the time to fill out this form!
+
+        - For questions, ask in [Discussions](https://github.com/flamego/flamego/discussions).
+        - Before you file an issue read the [Contributing guide](https://github.com/flamego/flamego/blob/main/.github/contributing.md).
+        - Check to make sure someone hasn't already opened a similar [issue](https://github.com/flamego/flamego/issues).
   - type: textarea
     attributes:
       label: What needs to improved? Please describe

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -6,6 +6,10 @@ body:
     attributes:
       value: |
         Thanks for taking the time to fill out this form!
+
+        - For questions, ask in [Discussions](https://github.com/flamego/flamego/discussions).
+        - Before you file an issue read the [Contributing guide](https://github.com/flamego/flamego/blob/main/.github/contributing.md).
+        - Check to make sure someone hasn't already opened a similar [issue](https://github.com/flamego/flamego/issues).
   - type: dropdown
     attributes:
       label: Component
@@ -18,7 +22,7 @@ body:
   - type: input
     attributes:
       label: Middleware
-      description: If this is for middleware, please specify the repository URL, e.g. "https://github.com/flamego/template".
+      description: If this is for middleware, please specify the repository URL, e.g. "https://github.com/flamego/template". Otherwise, put "n/a".
       value: "https://github.com/flamego/"
     validations:
       required: false

.github/contributing.md

@@ -0,0 +1,58 @@
+# Welcome to Flamego contributing guide
+
+Thank you for investing your time in contributing to our projects!
+
+Read our [Code of Conduct](https://go.dev/conduct) to keep our community approachable and respectable.
+
+In this guide you will get an overview of the contribution workflow from opening an issue, creating a PR, reviewing, and merging the PR.
+
+Use the table of contents icon <img src="https://github.com/github/docs/raw/50561895328b8f369694973252127b7d93899d83/assets/images/table-of-contents.png" width="25" height="25" /> on the top left corner of this document to get to a specific section of this guide quickly.
+
+## New contributor guide
+
+To get an overview of the project, read the [README](/README.md). Here are some resources to help you get started with open source contributions:
+
+- [Finding ways to contribute to open source on GitHub](https://docs.github.com/en/get-started/exploring-projects-on-github/finding-ways-to-contribute-to-open-source-on-github)
+- [Set up Git](https://docs.github.com/en/get-started/quickstart/set-up-git)
+- [GitHub flow](https://docs.github.com/en/get-started/quickstart/github-flow)
+- [Collaborating with pull requests](https://docs.github.com/en/github/collaborating-with-pull-requests)
+
+In addition to the general guides with open source contributions, you would also need to:
+
+- Have basic knowledge about HTTP, web applications development and programming in [Go](https://go.dev/).
+- Have a working local development setup with a reasonable good IDE or editor like [Visual Studio Code](https://code.visualstudio.com/docs/languages/go), [GoLand](https://www.jetbrains.com/go/) or [Vim](https://github.com/fatih/vim-go).
+
+## Issues
+
+### Create a new issue
+
+- For questions, ask in [Discussions](https://github.com/flamego/flamego/discussions).
+- [Check to make sure](https://docs.github.com/en/github/searching-for-information-on-github/searching-on-github/searching-issues-and-pull-requests#search-by-the-title-body-or-comments) someone hasn't already opened a similar [issue](https://github.com/flamego/flamego/issues).
+- If a similar issue doesn't exist, open a new issue using a relevant [issue form](https://github.com/flamego/flamego/issues/new/choose).
+
+### Pick up an issue to solve
+
+- Scan through our [existing issues](https://github.com/flamego/flamego/issues) to find one that interests you.
+- The [👋 good first issue](https://github.com/flamego/flamego/issues?q=is%3Aissue+is%3Aopen+label%3A%22%F0%9F%91%8B+good+first+issue%22) is a good place to start exploring issues that are well-groomed for newcomers
+- Please do not hesitate to ask for more details or clarifying questions on the issue!.
+- Every issue that gets picked up will have an expected timeline for the implementation, the issue may be reassigned after the expected timeline. Please be responsible and proactive on the communication 🙇‍♂️
+
+## Pull requests
+
+When you're finished with the changes, create a pull request, or a series of pull requests if necessary.
+
+Contributing to another codebase is not as simple as code changes, it is also about contributing influence to the design. Therefore, we kindly ask you that:
+
+- Please acknowledge that no pull request is guaranteed to be merged.
+- Please always do a self-review before requesting reviews from others.
+- Please expect code review to be strict and may have multiple rounds.
+- Please make self-contained incremental changes, pull requests with huge diff may be rejected for review.
+
+### Add middleware to the Flamego organization
+
+- New middleware require proposals before we may be able to accept any contribution.
+- Transfer middleware to the Flamego organization is currently not encouraged.
+
+## Your PR is merged!
+
+Congratulations 🎉🎉 Thanks again for taking the effort to have this journey with us 🌟

.github/pull_request_template.md

@@ -6,6 +6,6 @@ Link to the issue: <!-- paste the issue link here, or put "n/a" if not applicabl
 
 ### Checklist
 
-- [ ] I agree to follow this project's [Code of Conduct](https://go.dev/conduct) by submitting this pull request.
-- [ ] I totally understand sending a pull request has no guarantee to be merged, and the review rounds may take a long time.
+- [ ] I agree to follow the [Code of Conduct](https://go.dev/conduct) by submitting this pull request.
+- [ ] I have read and acknowledge the [Contributing guide](https://github.com/flamego/flamego/blob/main/.github/contributing.md).
 - [ ] I have added test cases to cover the new code.