Add HAML linting GitHub Action step

.github/workflows/retrospring.yml

@@ -67,6 +67,8 @@ jobs:
         env:
           POSTGRES_PORT: ${{ job.services.postgres.ports[5432] }}
           REDIS_URL: "redis://localhost:${{ job.services.redis.ports[6379] }}"
+      - name: Lint HAML templates
+        run: bundle exec haml-lint app/views
       - uses: codecov/codecov-action@v1
         with:
           token: ${{ secrets.CODECOV_TOKEN }}