Add GitHub workflow to check pull requests for DCO

Signed-off-by: Stefan Weil <sw@weilnetz.de>

Author: stweil

.github/workflows/dco.yml

@@ -0,0 +1,22 @@
+# .github/workflows/dco.yml
+name: DCO
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python 3.x
+      uses: actions/setup-python@v4
+      with:
+        python-version: '3.x'
+    - name: Check DCO
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run: |
+        pip3 install -U dco-check
+        dco-check