Add discussion templates

[aegis301]

Add discussion templates for new product ideas, as well as new feature ideas

[felixevers]

Recently added by GitHub see: #2838
https://github.blog/2023-01-09-github-discussions-just-got-better-with-category-forms/

[felixevers]

Please wait for #8 which implements a basic discussion template.

[felixevers]

#8 merged.