Add link to the repo within the frontend.

To increase the transparency of our development, I would like to add a link to the repo in the sms frontend.

I would like to have something like the link to the gitlab on the bottom of the mattermost page:

https://mattermost.com/

(But in general I would love to have those icons also on the top bar - which is also quite common - but I didn't find an example for this on the moment)