chore(angularFiles): add documentation only file to list of files

This prevents errors when checking `validate-angular-files`

Author: petebacondarwin

angularFiles.js

@@ -32,6 +32,7 @@ var angularFiles = {
     'src/ng/q.js',
     'src/ng/raf.js',
     'src/ng/rootScope.js',
+    'src/ng/rootElement.js',
     'src/ng/sanitizeUri.js',
     'src/ng/sce.js',
     'src/ng/sniffer.js',