Add Dependabot configuration

.github/dependabot.yml

@@ -0,0 +1,34 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
+  - package-ecosystem: "nuget"
+    directories:
+      - "/**"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    groups:
+      nuget:
+        patterns:
+          - "*"
+        group-by: dependency-name
+
+  - package-ecosystem: "npm"
+    directories:
+      - "/**"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    groups:
+      npm:
+        patterns:
+          - "*"
+        group-by: dependency-name

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

@@ -0,0 +1,28 @@
+name: dependabot
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' && github.repository_owner == 'dotnet' && github.base_ref == 'main' }}
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - name: Auto-approve PR
+        run: gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+
+      - name: Auto-merge PR
+        run: gh pr merge --auto --squash "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}