feat: app store app documentation template (#829)

* docs: 🚧 add work in progress template

* update

* Update TEMPLATE.md

* Update TEMPLATE.md

* extend documentation template

---------

Co-authored-by: Lukasz Ostrowski <lukasz.ostrowski@saleor.io>

docs/developer/app-store/apps/TEMPLATE.mdx

@@ -0,0 +1,119 @@
+# App Name
+
+## Metadata
+
+<!--
+TODO React component with a badges / toolbar with the following:
+ -->
+
+- Saleor version
+- Roadmap
+- Link to dashboard
+- Link to GitHub
+
+## Introduction
+
+<!--
+Explain problem the app solves. Outline basic context and use cases.
+-->
+
+## Features
+
+<!--
+Highlight the most important features of the app. Mention available providers if any.
+If some feature is more complicated, create a dedicated page with more details or a dedicated guide.
+
+Add upcoming featuers with link to roadmap/github, allowing reader to vote or comment.
+-->
+
+## Assumptions & limitations
+
+<!--
+Outline assumptions and limitations of the app. What is a planned scope, what is out of scope.
+Mention know problems and limitations. If possible link to github where errors and tasks are tracked.
+-->
+
+## Glossary
+
+<!--
+Describe terms used in the app. If there are no specific language, skip this chapter.
+-->
+
+## Permissions
+
+<!--
+Describe what permissions app needs and why. If permissions are granted dynamically, mention when and what happens if they are missing.
+
+Also describe how logged dashboard user's permissions affect app's behavior. For exampl "MANAGE_APPS" needed to save app configuration.
+
+-->
+
+## Application flow
+
+<!--
+Describe how app works. Mention all webhooks app listens to and what happens when they are triggered.
+Draw a diagram if needed.
+Nest pages is some complex explanations are required
+-->
+
+## Pre-requisites
+
+<!--
+Global steps required to start using the app.
+-->
+
+## Configuration
+
+<!--
+Global configuration of the app
+-->
+
+### Provider specific configuration
+
+<!--
+If app has many providers, we assume most users will use one of them.
+
+Mention here all the details required to configure this provider.
+Mention provider-specific testing.
+-->
+
+### Testing
+
+<!--
+If applies, mention how to test if app works
+-->
+
+## Troubleshooting
+
+<!--
+Mention know issues
+-->
+
+### Errors index
+
+<!--
+List common errors that app can throw. If app returns some error code, it can be
+put here with details instructions.
+-->
+
+## Development
+
+<!--
+Link to develoment guide common for every apps.
+
+Then include specific development guide for this app.
+
+Mention all env variables
+-->
+
+## Contributing
+
+<!--
+Link to contributing guides shared for all apps
+-->
+
+## Community resources
+
+<!--
+If any, list resources created by community.
+-->