Add touchy-pad plugin

[geeksville]

Add the touchy-pad plugin to the store.

[nekename]

The repo URL you've added to the catalogue is a 404. Also, the description in the catalogue doesn't match the description of your actual repo

[geeksville]

@nekename oops! Sorry about the URL typo, fixed!

I'm not quite sure how to handle "Also, the description in the catalogue doesn't match the description of your actual repo". The description I used in the 'store' I tried to pick how touchy-pad would be perceived by OpenDeck users. Do you want it to match the more general description I use in the README (which has various additional applications)?

[nekename]

It just needs to match the short-description of the repo, i.e. An open-source graphical touchpad/macropad project. You could change that description if you want something else rendered here (although the description property in the catalogue isn't even used anywhere yet)

[geeksville]

oh I see! The github short-description! I'll change the catalog.json to match.