.github: add checklist to PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,13 +1,28 @@
+
+This pull request includes:
+
+- [ ] adequate testing for the new functionality or fixed issue
+- [ ] adequate documentation informing people about the change
+
 <!--
 Thanks for proposing a change to osbuild-composer!
 
-If this pull request fixes a downstream issue, please refer to test/README.md
-and uncomment this checklist:
+Please don't remove the above check list. These are things that each pull
+request must have before it is merged. It helps maintainers to not forget
+anything.
+
+If the reason for ticking any of the boxes is ambiguous, please add a short
+note explaining why.
+
+For user-visible changes, "adequate documentation" is an entry describing the
+change for users in docs/news. Please refer to docs/news/README.md for details.
+
+In addition, if this pull request fixes a downstream issue, please refer to
+test/README.md and add these additional items:
 
 - [ ] 1st commit of any `rhbz#` related PR contains bug reproducer; CI reports FAIL or
 - [ ] PR contains automated tests for new functionality and
 - [ ] QE has approved reproducer/new tests and
 - [ ] Subsequent commits provide bug fixes without modifying the reproducer; CI reports PASS and
 - [ ] QE approves this PR; RHBZ status is set to `MODIFIED + Verified=Tested`
-
 -->