Conditionally auto-approve dependabot PRs

We want to set up a flow to to auto-approve some dependabot PRs. PRs will only
be approved if:
- they are not `npm` updates, and
- the update is only a version patch

Author: cadmiumcat

.github/workflows/dependabot-auto-approve.yml

@@ -0,0 +1,26 @@
+name: Dependabot auto-approve
+on: pull_request
+permissions:
+  pull-requests: write
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    # Checking the author will prevent your Action run failing on non-Dependabot PRs
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
+    steps:
+      - name: Dependabot metadata
+        id: dependabot-metadata
+        uses: dependabot/fetch-metadata@v2
+      - uses: actions/checkout@v4
+      - name: Approve a PR if not already approved
+      # as long as it's not a npm PR, and the update is a patch version
+        if: "!contains(steps.dependabot-metadata.outputs.package-ecosystem, 'npm') && steps.dependabot-metadata.outputs.update-type == 'version-update:semver-patch'"
+        run: |
+          gh pr checkout "$PR_URL" # sets the upstream metadata for `gh pr status`
+          if [ "$(gh pr status --json reviewDecision -q .currentBranch.reviewDecision)" != "APPROVED" ];
+          then gh pr review --approve "$PR_URL"
+          else echo "PR already approved, skipping additional approvals to minimize emails/notification noise.";
+          fi
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}