chore: add pr template

[MicaiahReid]

PR description

This PR introduces a PR template that will be used to guide contributors on a format for creating PRs in the Ganache repo. Fixes #3758

We can bike shed this to our heart's content, but I figured I'd get something out to start the conversation. By the way, this PR description uses the template.

Testing instructions

N/A

Documentation

• [ ] I've added the doc-change-required label to this PR so that documentation can be added by the docs team in another PR.
• [ ] I've included documentation changes in this PR:
  • [ ] I've updated the README.md.
  • [ ] I've updated the CONTRIBUTING.md.
  • [ ] I've added/updated an RPC method in src/chains/ethereum/ethereum/RPC-METHODS.md.
  • [ ] I've added/updated a JS-DOC example of a new RPC method in src/chains/ethereum/ethereum/src/api.ts.
• [X] This PR does not require documentation changes.
• [x] I don't know what this PR needs in regards to documentation.

Release Notes

This change introduces a PR template that will be used to guide contributors on a format for creating PRs in the Ganache repo.

[MicaiahReid]

I've rearranged a bit and added some further comments to make very clear that most of the information is optional for external contributors. @davidmurdoch's concern is that these templates will be a barrier to entry or an annoyance for some contributors, and we definitely don't want that. Input welcome.

[davidmurdoch]

I don't like it :-/

[MicaiahReid]

Seems like this isn't something we think is best for us right now.