docs($document): add a documentation example.
docs($document): add a documentation example.

The $document docs are pretty empty, and this fills them out a bit. The example itself may not be
particularly useful, but it could be improved or removed later. Works for me.

Closes #6757

ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js