docs: update PR template (#2215)

* docs: update PR template

* docs: incorporate suggestions from PR review

Author: bradenmacdonald

.github/pull_request_template.md

@@ -2,26 +2,37 @@
 
 Describe what this pull request changes, and why. Include implications for people using this change.
 Design decisions and their rationales should be documented in the repo (docstring / ADR), per
+[OEP-19](https://open-edx-proposals.readthedocs.io/en/latest/oep-0019-bp-developer-documentation.html), and can be linked here.
 
 Useful information to include:
-- Which edX user roles will this change impact? Common user roles are "Learner", "Course Author",
+- Which user roles will this change impact? Common user roles are "Learner", "Course Author",
 "Developer", and "Operator".
 - Include screenshots for changes to the UI (ideally, both "before" and "after" screenshots, if applicable).
-- Provide links to the description of corresponding configuration changes. Remember to correctly annotate these
-changes.
 
 ## Supporting information
 
-Link to other information about the change, such as Jira issues, GitHub issues, or Discourse discussions.
+Link to other information about the change, such as GitHub issues, or Discourse discussions.
 Be sure to check they are publicly readable, or if not, repeat the information here.
 
 ## Testing instructions
 
-Please provide detailed step-by-step instructions for testing this change.
-
+Please provide detailed step-by-step instructions for manually testing this change.
 
 ## Other information
 
 Include anything else that will help reviewers and consumers understand the change.
 - Does this change depend on other changes elsewhere?
-- Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.
+- Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.
+
+## Best Practices Checklist
+
+We're trying to move away from some deprecated patterns in this codebase. Please
+check if your PR meets these recommendations before asking for a review:
+
+- [ ] Any _new_ files are using TypeScript (`.ts`, `.tsx`).
+- [ ] Deprecated `propTypes`, `defaultProps`, and `injectIntl` patterns are not used in any new or modified code.
+- [ ] Tests should use the helpers in `src/testUtils.tsx` (specifically `initializeMocks`)
+- [ ] Do not add new fields to the Redux state/store. Use React Context to share state among multiple components.
+- [ ] Use React Query to load data from REST APIs. See any `apiHooks.ts` in this repo for examples.
+- [ ] All new i18n messages in `messages.ts` files have a `description` for translators to use.
+- [ ] Imports avoid using `../`. To import from parent folders, use `@src`, e.g. `import { initializeMocks } from '@src/testUtils';` instead of `from '../../../../testUtils'`