chore(ci): add coverage comment step

.github/workflows/tests-pytest.yml

@@ -5,6 +5,14 @@ on: [push, pull_request]
 jobs:
   pytest:
     runs-on: ubuntu-latest
+    permissions:
+      # Gives the action the necessary permissions for publishing new
+      # comments in pull requests.
+      pull-requests: write
+      # Gives the action the necessary permissions for pushing data to the
+      # python-coverage-comment-action branch, and for editing existing
+      # comments (to avoid publishing multiple comments in the same PR)
+      contents: write
     steps:
       - name: Check out code
         uses: actions/checkout@v4
@@ -34,3 +42,10 @@ jobs:
         with:
           name: coverage-report
           path: benefits/static/coverage
+
+      - name: Coverage comment
+        uses: py-cov-action/python-coverage-comment-action@v3
+        with:
+          GITHUB_TOKEN: ${{ github.token }}
+          MINIMUM_GREEN: 90
+          MINIMUM_ORANGE: 80