chore: add issue template config.yml

[dennishzg]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

I added the new issue template configuration options. Awesome new feature 🎉

You can customize the issue template chooser that people see when creating a new issue in your repository by adding a config.yml file to the .github/ISSUE_TEMPLATE folder.

If you prefer to receive certain reports outside of GitHub, you can direct people to external sites with contact_links.

You can require contributors to use issue templates by setting blank_issue_enabled to false. If you set blank_issue_enabled to true, people will have the option to open a blank issue.

Links:

• https://help.github.com/en/github/building-a-strong-community/configuring-issue-templates-for-your-repository#configuring-the-template-chooser
• https://github.blog/changelog/2019-10-28-new-issue-template-configuration-options/

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information: