ci: add auto-merge

Author: gauteh

.github/workflows/auto-merge.yml

@@ -0,0 +1,19 @@
+name: Codeowners auto-merge
+on:
+  pull_request_target: { types: [opened] }
+  issue_comment: { types: [created] }
+  pull_request_review: { types: [submitted] }
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run Codeowners merge check
+        uses: OSS-Docs-Tools/code-owner-self-merge@1.6.8
+        with:
+          if_no_maintainers_add_label: 'maintainers'
+          if_no_maintainers_assign: '@knutfrode @gauteh'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}