_playsupportedLocalStorage is not on properties

I stumbled this issue while linting a component that is using google-youtube.
../bower_components/google-youtube/google-youtube.html:98:7
    Property '_playsupportedLocalStorage' bound to attribute 'value' not found in 'properties' for element 'google-youtube'

Just add _playsupportedLocalStorage to the component properties.

Thank you.
