Add css lint config and GitHub action, fix issues

.github/workflows/lint-frontend.yml

@@ -0,0 +1,30 @@
+name: Static Analysis (Linting)
+
+# This workflow is triggered on pushes to trunk, and any PRs.
+on:
+  push:
+    branches: [master]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install NodeJS
+      uses: actions/setup-node@v4
+      with:
+        node-version-file: '.nvmrc'
+        cache: 'npm'
+
+    - name: npm install and build
+      run: |
+        npm ci
+        npm run build
+
+    - name: Lint JavaScript and Styles
+      run: |
+        npm run lint:css

package.json

@@ -32,6 +32,7 @@
   "homepage": "https://github.com/Automattic/meeting-calendar#readme",
   "devDependencies": {
     "@wordpress/env": "9.7.0",
-    "@wordpress/scripts": "27.9.0"
+    "@wordpress/scripts": "27.9.0",
+    "@wordpress/stylelint-config": "21.34.0"
   }
 }