### Description of proposed changes
What is the goal of this pull request? What does this pull request change?

### Related issue(s)
<!-- Start typing the name of a related issue and GitHub will auto-suggest the issue number for you.  -->
Fixes #
Related to #

### Testing
What steps should be taken to test the changes you've proposed?
If you added or changed behavior in the codebase, did you update the tests, or do you need help with this?

<!-- 🙌 Thank you for contributing to Nextstrain! ✨ -->

Copy PR template from nextstrain/.github
Copy PR template from nextstrain/.github

Copy it here so we can make edits specific for the Augur repo use case.

https://github.com/nextstrain/.github/blob/24efb1981ec34b188535da9b1307076a06c1f3f3/.github/pull_request_template.md
