Update pull_request_template.md

Added requirement that PRs contain a description

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

@@ -4,10 +4,12 @@ about: Create a pull request
 label: 'triage me'
 ---
 Thank you for opening a Pull Request!
-Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
-- [ ] Make sure to open a GitHub issue as a bug/feature request before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
+Before submitting your PR, please make sure you:
+
+- [ ] Include a PR description which states **what you've done and why**
+- [ ] Open a GitHub issue as a bug/feature request before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
 - [ ] Ensure the tests and linter pass (`./gradlew --init-script gradle/init.gradle.kts spotlessApply` to automatically apply formatting)
-- [ ] Appropriate docs were updated (if necessary)
+- [ ] Update any relevant documentation
 
 Is this your first Pull Request?
 - [ ] Run `./tools/setup.sh`