PR template migrations note (#2496)

* Add item on migration files to PR template.

* Add item on migration files to PR template.

* Add item on migration files to PR template.

* Add item on migration files to PR template.

.github/pull_request_template.md

@@ -5,6 +5,7 @@
 - [ ]   List any special steps reviewers have to follow to test the PR. For example, adding a local environment variable, creating a local test file, etc.
 - [ ]   For extra credit, submit a screen recording like [this one](https://github.com/GSA-TTS/FAC/pull/1821).
 - [ ]   Make sure you’ve merged `main` into your branch shortly before creating the PR. (You should also be merging `main` into your branch regularly during development.)
+- [ ]   Make sure you’ve accounted for any migrations. When you’re about to create the PR, bring up the application locally and then run `git status | grep migrations`. If there are any results, you probably need to add them to the branch for the PR. Your PR should have only **one** new migration file for each of the component apps, except in rare circumstances; you may need to delete some and re-run `python manage.py makemigrations` to reduce the number to one. (Also, unless in exceptional circumstances, your PR should not delete any migration files.)
 - [ ]   Make sure that whatever feature you’re adding has tests that cover the feature. This includes test coverage to make sure that the previous workflow still works, if applicable.
 - [ ]   Do manual testing locally. Our tests are not good enough yet to allow us to skip this step. If that’s not applicable for some reason, check this box.
 - [ ]   Verify that no Git surgery was necessary, or, if it was necessary at any point, repeat the testing after it’s finished.