Course automation submission: Checking legal group composition (#1131)

* Feat Adds yml file that calls group-validity-action

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Update README.md

.github/workflows/groupValidity.yml

@@ -0,0 +1,25 @@
+name: Group validity check
+on:
+  pull_request_target:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Get file added in the pullrequest
+        id: file_changes
+        uses: trilom/[email protected]
+      - id: getPayload
+        run: |
+          payload=$(cat $GITHUB_EVENT_PATH)
+          payload="${payload//'%'/'%25'}"
+          payload="${payload//$'\n'/'%0A'}"
+          payload="${payload//$'\r'/'%0D'}"
+          echo "::set-output name=payload::$payload"
+      - uses: EleonoraBorzis/group-validity-action@main
+        with: 
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          payload:  ${{ steps.getPayload.outputs.payload }}
+          filesAdded: ${{ steps.file_changes.outputs.files_added}}
+          basefolder: contributions/ 
+          maxGroupSize: 3 
+          maxCollaborationTimes: 2