Add a link to the wiki to make screenshots

[Cqoicebordel]

On https://watchy.sqfmi.com/docs/create-watchface/, there are a lots of nice explanation, but none on how to make a screenshot of the Watchy.

It took me way too long to find the wiki article explaining how to : https://github.com/sqfmi/Watchy/wiki/Screenshots-of-Watchfaces

So, a link should be added to it on the official site, to make sure it's easily findable.

[sqfmi]

Thanks for the feedback! Will add it to the docs