docs(directive/input): document ngTrim for textarea

src/ng/directive/input.js

@@ -749,6 +749,7 @@ function checkboxInputType(scope, element, attr, ctrl) {
  *    patterns defined as scope expressions.
  * @param {string=} ngChange Angular expression to be executed when input changes due to user
  *    interaction with the input element.
+ * @param {boolean=} [ngTrim=true] If set to false Angular will not automatically trim the input.
  */