add missing permissions for coverage action

.github/workflows/ci.yml

@@ -13,7 +13,14 @@ jobs:
   build:
 
     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:
     - uses: actions/checkout@v3
     - name: Set up Python 3.10