ci: Prevent concurrent CI runs (#515)

Author: mtrezza

.github/workflows/ci.yml

@@ -60,3 +60,6 @@ jobs:
         env:
           CI: true
       - run: bash <(curl -s https://codecov.io/bash)
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true