Introducing discussion category forms

[gh640]

GitHub made discussion category forms available in Jan 2023.

• https://github.blog/2023-01-09-github-discussions-just-got-better-with-category-forms/
• https://docs.github.com/en/discussions/managing-discussions-for-your-community/creating-discussion-category-forms

Using the function in this repository may be useful as in issue templates.

The PR for issue templates:

• chore: Use Issue Forms templates #32157