link to https://github.com/unisonweb/unison on webpage

[hejfelix]

Normally, there's a prominent link to the github page for contributors and interested people.
Currently, there's only a small link to this repo. Would be nice to be directed directly to the "meat" of it all.

[pchiusano]

It is linked from the home page, but you have scroll down a little (see below). Maybe we can make it more prominent or make it a top toolbar link like the blog and docs links.

[chiroptical]

Is this a change you would like to make on the website? I believe I just need to modify src/data/layouts/partials/site-nav.yml with the new link.