ci: Add dependabot auto build support (#5)

.github/workflows/auto-build.yml

@@ -0,0 +1,33 @@
+name: Dependabot Auto Build
+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 }}"
+
+      - name: Set up Go 1.x
+        uses: actions/setup-go@v2
+        with:
+          go-version: "1.15"
+
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Auto build
+        run: make build
+
+      - name: Auto commit
+        uses: EndBug/add-and-commit@v7
+        with:
+          default_author: github_actions