build(aio): move doc-gen stuff from angular.io (#14097)

tools/docs/angular.io-package/processors/extractDecoratedClasses.js

@@ -0,0 +1,29 @@
+var _ = require('lodash');
+
+module.exports = function extractDecoratedClassesProcessor(EXPORT_DOC_TYPES) {
+
+  // Add the "directive" docType into those that can be exported from a module
+  EXPORT_DOC_TYPES.push('directive', 'pipe');
+
+  return {
+    $runAfter: ['processing-docs'],
+    $runBefore: ['docs-processed'],
+    decoratorTypes: ['Directive', 'Component', 'Pipe'],
+    $process: function(docs) {
+      var decoratorTypes = this.decoratorTypes;
+
+      _.forEach(docs, function(doc) {
+
+        _.forEach(doc.decorators, function(decorator) {
+
+          if (decoratorTypes.indexOf(decorator.name) !== -1) {
+            doc.docType = decorator.name.toLowerCase();
+            doc[doc.docType + 'Options'] = decorator.argumentInfo[0];
+          }
+        });
+      });
+
+      return docs;
+    }
+  };
+};