|url||The (full) URL for the overlay to open.|
with this function you can open the Steam game overlay to its
web browser and then have it load the specified URL. you need to
use the full URL as a string for this to resolve correctly,
for example: "http://www.steamgames.com/".
The above code polls the keyboard for the F1 key and if it is then Steam overlay will be opened and resolve to the given URL.