Add issue templates for the repository

[noahsprent]

A lot of our issues don't necessarily have the right labels, or aren't that clear. One way to help with this is to use templates for the issues. We should implement the default templates for enhancements and bugs, and add our own for 'Good First Issue' and package requests (see #88). For this issue:

• Add default GitHub templates for enhancements and bugs
• Add a custom template for 'Good first issue' issues

GitHub instructions here:
https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository

[noahsprent]

In the spirit of not letting the perfect be the enemy of the good, I have added some templates for now, which need improvement.