Update PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,17 +1,28 @@
-**Thanks for contributing to Prefect!**
+<!-- Thanks for contributing to Prefect Core! 🎉-->
 
-Please describe your work and make sure your PR:
+## Summary
+<!-- A sentence summarizing the PR -->
 
-- [ ] adds new tests (if appropriate)
-- [ ] add a changelog entry in the `changes/` directory (if appropriate)
-- [ ] updates docstrings for any new functions or function arguments, including `docs/outline.toml` for API reference docs (if appropriate)
 
-Note that your PR will not be reviewed unless all three boxes are checked.
 
-## What does this PR change?
+
+## Changes
+<!-- What does this PR change? -->
+
+
 
 
+## Importance
+<!-- Why is this PR important? -->
 
-## Why is this PR important?
 
 
+
+## Checklist
+<!-- PRs will not be reviewed unless these boxes are checked -->
+
+This PR:
+
+- [ ] adds new tests (if appropriate)
+- [ ] adds a change file in the `changes/` directory (if appropriate)
+- [ ] updates docstrings for any new functions or function arguments, including `docs/outline.toml` for API reference docs (if appropriate)