Run rubocop checks as part of CI

.gitea/workflows/tests.yml

@@ -1,4 +1,4 @@
-name: Run unit tests
+name: Run unit tests and Rubocop
 on:
   push:
     branches:
@@ -24,6 +24,7 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
       - uses: ruby/setup-ruby@v1.202.0
       - run: bundle install
+      - run: bundle exec rubocop --force-exclusion --parallel
       - name: Wait until Postgres is ready to accept connections
         run: |
           apt-get update && apt-get install -f -y postgresql-client