CI: Add dependabot auto-merge

Signed-off-by: Andrej Orsula <[email protected]>

.github/workflows/dependabot.yml

@@ -0,0 +1,29 @@
+name: Dependabot auto-merge
+on:
+  pull_request:
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - name: Fetch metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v1
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Approve PR
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}
+        run: gh pr review --approve "$PR_URL"
+      - name: Enable auto-merge
+        if: steps.metadata.outputs.update-type == 'version-update:semver-patch'
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}
+        run: gh pr merge --auto --merge "$PR_URL"