feat(navigation): add prominent validation quickstart action

validation-suite/frontend/atlas/node_modules/postcss/lib/rule.js

@@ -0,0 +1,27 @@
+'use strict'
+
+let Container = require('./container')
+let list = require('./list')
+
+class Rule extends Container {
+  get selectors() {
+    return list.comma(this.selector)
+  }
+
+  set selectors(values) {
+    let match = this.selector ? this.selector.match(/,\s*/) : null
+    let sep = match ? match[0] : ',' + this.raw('between', 'beforeOpen')
+    this.selector = values.join(sep)
+  }
+
+  constructor(defaults) {
+    super(defaults)
+    this.type = 'rule'
+    if (!this.nodes) this.nodes = []
+  }
+}
+
+module.exports = Rule
+Rule.default = Rule
+
+Container.registerRule(Rule)