ci(style): ensure PRs follow code style (#258)

Author: coderbyheart

.eslintrc

@@ -1,5 +1,3 @@
 {
-    "extends": [
-        "./index.js"
-    ]
-}
+  "extends": ["./index.js"]
+}

.github/workflows/code-style.yaml

@@ -0,0 +1,48 @@
+name: Ensure source code is properly formatted
+
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  style:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+
+      - uses: actions/setup-node@v3
+        with:
+          node-version: "16.x"
+
+      - name: Keep npm cache around to speed up installs
+        uses: actions/cache@v3
+        with:
+          path: ~/.npm
+          key: ${{ runner.OS }}-build-${{ hashFiles('**/package-lock.json') }}
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Format source code with prettier
+        run: npx prettier --write ./
+
+      - name: Check source code with eslint
+        run: npx eslint --fix --ext .js,.ts,.jsx,.tsx --ignore-pattern commitlint.config.js --ignore-path .gitignore ./
+
+      - name: Commit changes
+        run: |
+          if ! git diff --exit-code --name-only; then
+            echo "machine github.com login accesskey password ${{ secrets.GITHUB_TOKEN }}" > ~/.netrc
+            git config --global user.email "[email protected]"
+            git config --global user.name "GitHub Actions"
+            git add -A
+            git commit -m "style: ensure source code is properly formatted"
+            git push origin HEAD:${{ github.event.pull_request.head.ref }}
+          fi