docs(compile): document $attrs.$normalize

Closes #10345

src/ng/compile.js

@@ -653,6 +653,21 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
     };
 
     Attributes.prototype = {
+      /**
+       * @ngdoc method
+       * @name $compile.directive.Attributes#$normalize
+       * @kind function
+       *
+       * @description
+       * Converts an attribute name (e.g. dash/colon/underscore-delimited string, optionally prefixed with `x-` or
+       * `data-`) to its normalized, camelCase form.
+       *
+       * Also there is special case for Moz prefix starting with upper case letter.
+       *
+       * For further information check out the guide on {@link guide/directive#matching-directives Matching Directives}
+       *
+       * @param {string} name Name to normalize
+       */
       $normalize: directiveNormalize,
 
 
@@ -1986,13 +2001,6 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
 var PREFIX_REGEXP = /^(x[\:\-_]|data[\:\-_])/i;
 /**
  * Converts all accepted directives format into proper directive name.
- * All of these will become 'myDirective':
- *   my:Directive
- *   my-directive
- *   x-my-directive
- *   data-my:directive
- *
- * Also there is special case for Moz prefix starting with upper case letter.
  * @param name Name to normalize
  */
 function directiveNormalize(name) {