chore: ci lint automation (#2) (#7)

github actions를 이용한 lint automation 진행.
markdownlint만 추가.

.github/workflows/lint.yaml

@@ -0,0 +1,34 @@
+name: lint
+
+on:
+  push:
+    branches: [main]
+
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Set up checkout
+        uses: actions/checkout@v4
+
+      - name: Set up node
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: .nvmrc
+          cache: npm
+
+      - name: Set up cache
+        uses: actions/cache@v4
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
+
+      - name: Set up node_modules
+        run: npm ci
+
+      - name: Lint markdownlint
+        run: npm run lint-markdownlint