Add stylelint to GitHub Actions workflow to lint the CSS (closes #80)

---------

Co-authored-by: Postmodern <[email protected]>

.github/workflows/stylelint.yml

@@ -0,0 +1,22 @@
+name: Lint CSS
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install stylelint
+        run: npm install -g stylelint stylelint-config-standard
+
+      - name: Run stylelint
+        run: stylelint stylesheets/*.css

.stylelintrc.json

@@ -0,0 +1,3 @@
+{
+  "extends": "stylelint-config-standard"
+}

stylesheets/print.css

@@ -40,4 +40,4 @@ object.demo {
 
 article.post .post-links {
     display: none;
-}
+}