Add more docs and placeholder newsfragment.

.github/workflows/ci.yml

@@ -235,11 +235,19 @@ jobs:
         password: ${{ secrets.PYPI_TOKEN }}
         verbose: true
 
+  # This is a meta-job to simplify PR CI enforcement configuration in GitHub.
+  # Inside the GitHub config UI you only configure this job as required.
+  # All the extra requirements are defined "as code" as part of the `needs`
+  # list for this job.
   all:
     name: All success
     runs-on: ubuntu-latest
+    # The always() part is very important.
+    # If not set, the job will be skipped on failing dependencies.
     if: always()
     needs:
+      # This is the list of CI job that we are interested to be green before
+      # a merge.
       - build
       - test-linux
       - test-windows