Added CI workflow

.github/workflows/frontend-ci.yml

@@ -0,0 +1,34 @@
+name: Frontend CI
+
+on:
+  push:
+    paths:
+      - "frontend/**"
+
+
+jobs:
+  prettier:
+    name: Code quality check
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18, 20]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: "npm"
+          cache-dependency-path: ./frontend/package-lock.json
+
+      - name: Clean install
+        working-directory: ./frontend
+        run: npm ci
+
+      - name: Prettier & Eslint
+        working-directory: ./frontend
+        run: npm run lint
+
+      - name: Svelte check
+        working-directory: ./frontend
+        run: npm run check