Added Git to on_boarding

docs/on_boarding.md

@@ -60,6 +60,12 @@ Joining the MEDLab Space:
     
 -   Choose which rooms you want to join by pressing the compass button right under your name in the top-left of the web interface. Be sure you're in #general, as well as the rooms related to any projects you're part of or interested in.
 
+### Git
+
+Gitea is an open-source, relatively simple implementation of the Git version-control system. It is similar to the commerical platforms GitHub and GitLab but easier to self-host and manage. We use it to manage the lab's software projects and other documentation (such as this Handbook). It is a useful way to collaborate on things that are too complex for the office tools on Nextcloud.
+
+If you're a MEDLab member, you can join the [MEDLab Contributors](https://git.medlab.host/org/MEDLab/teams/medlab_contributors) team, which gives you edit access to the main MEDLab repositories. If you need this access, let Nathan know.
+
 
 ## Website profile