fix: cancel in progress CI runs

This improves the CI experience as it will run the github checks in a
group and at the same time cancel in progress jobs if a new commit is
pushed for the pull request.

No only does it makes the contributing experience nice, but it also
saves tonnes of energy.

- Github Issue: #8276

Authored-by: Vinit Kumar <vinit.kumar@kidskonnect.nl>
Signed-off-by: Vinit Kumar <vinit.kumar@kidskonnect.nl>

.github/workflows/test.yml

@@ -1,5 +1,9 @@
 name: Wagtail CI
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 on:
   push:
     paths-ignore: