Create issue/discussion templates

[forsyth2]

Create issue/discussion templates so that when users create new issues or discussions, they will be guided on what information to provide. Examples:

https://github.com/xCDAT/xcdat/issues/new/choose
https://github.com/xCDAT/xcdat/discussions/new?category=2-questions

[forsyth2]

Resources:

• https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms
  • https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-githubs-form-schema
• https://github.com/xCDAT/xcdat/blob/main/.github/ISSUE_TEMPLATE/bug_report.yml?plain=1

[forsyth2]

Reopening since #480 was insufficient.

[forsyth2]

Reopening since #513 was insufficient.