Lint examples' CSS too.

docs/4.0/examples/.stylelintrc

@@ -0,0 +1,12 @@
+{
+  "extends": "../../../build/.stylelintrc",
+  "rules": {
+    "at-rule-no-vendor-prefix": null,
+    "comment-empty-line-before": null,
+    "media-feature-name-no-vendor-prefix": null,
+    "property-no-vendor-prefix": null,
+    "selector-no-qualifying-type": null,
+    "selector-no-vendor-prefix": null,
+    "value-no-vendor-prefix": null
+  }
+}

docs/4.0/examples/blog/blog.css

@@ -13,12 +13,18 @@ body {
   color: #555;
 }
 
-h1, .h1,
-h2, .h2,
-h3, .h3,
-h4, .h4,
-h5, .h5,
-h6, .h6 {
+h1,
+.h1,
+h2,
+.h2,
+h3,
+.h3,
+h4,
+.h4,
+h5,
+.h5,
+h6,
+.h6 {
   font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
   font-weight: 400;
   color: #333;