Incomplete list of keys in the documentation of set_keys

[Paolo Montrasio]

The documentation starting at

hound/lib/hound/helpers/page.ex

Line 229 in e10c872

   * :alt - alt key 

doesn't list all the keys supported by set_keys/1

I was looking for a way to send the right and left arrow keys to the browser, I kept reading the code and eventually found that set_keys/1 accepts any of the key codes defined at here and the following lines

hound/lib/hound/internal_helpers.ex

Line 27 in 7cfa0f8

 def key_code(:null),      do: "\\uE000" 

Luckily the arrow keys are among them.

Maybe the documentation of set_keys/1 should link to the source code with the definitions of key_codes/1
Any developer is able to read that and there would be no need to keep the documentation of set_keys/1 in sync with the code.