Add Dependabot Automation (#136)

* add dependabot configuration

* add workflow to auto-merge dependabot PRs

.github/dependabot.yml

@@ -0,0 +1,8 @@
+version: 2
+
+updates:
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

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

@@ -0,0 +1,40 @@
+name: dependabot-auto-merge
+on: pull_request_target
+
+permissions:
+  pull-requests: write
+  contents: write
+
+jobs:
+  dependabot:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/[email protected]
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+          compat-lookup: true
+
+      - name: Auto-merge Dependabot PRs for semver-minor updates
+        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-minor'}}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+
+      - name: Auto-merge Dependabot PRs for semver-patch updates
+        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-patch'}}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+
+      - name: Auto-merge Dependabot PRs for Action major versions when compatibility is higher than 90%
+        if: ${{steps.metadata.outputs.package-ecosystem == 'github_actions' && steps.metadata.outputs.update-type == 'version-update:semver-major' && steps.metadata.outputs.compatibility-score >= 90}}
+        run: gh pr merge --auto --merge "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}