Added suggestion for what to review to PR template

[malloryfreeberg]

Description

• Added section to PR template to request PR author provide suggestions for what reviewer should test/check/review.

Motivation and Context

By providing this information, the author can help reviewers know what they should be testing/checking/reviewing in the PR. It should not be an exhaustive list, but provide some hints for the reviewer.

How has this been tested?

Tested manually in PR #32.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change which adds new content)
• Modified content (non-breaking change which modifies existing content)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have read the CONTRIBUTING.md guide.
• My changes follow the code style of this project.
• I have updated supporting documentation, if required.
• I have added my details to the CONTRIBUTORS.yaml file.

[M-casado]

Good addition 👍