Improve this Doc

# Error: ng:btstrpd
App Already Bootstrapped with this Element

    App already bootstrapped with this element '{0}'

## Description

Occurs when calling `angular.bootstrap` on an element that has already been bootstrapped.

This usually happens when you accidentally use both `ng-app` and `angular.bootstrap` to bootstrap an application.

    <html>
    ...
      <body ng-app="myApp">
        <script>
          angular.bootstrap(document.body, ['myApp']);
        </script>
      </body>
    </html>

Note that for bootstrapping purposes, the `<html>` element is the same as `document`, so the following will also throw an error.

    <html>
    ...
    <script>
      angular.bootstrap(document, ['myApp']);
    </script>
    </html>

You can also get this error if you accidentally load AngularJS itself more than once.

    <html ng-app>
      <head>
        <script src="angular.js"></script>

        ...

      </head>
      <body>

        ...

        <script src="angular.js"></script>
      </body>
    </html>