forking the official app is tricky because it’s such a fast-moving target that is unlikely to wanna merge such an addition down the road.
There are however efforts like this being discussed for unofficial clients: https://github.com/elk-zone/elk/discussions/3030
Gobo exists as a live open source example as well.
Unfortunately the middle of the venm diagram ‘atproto enthusiast/user’ and ‘ap enthusiast/user’ appears to be so small that no one has decided to pursue this yet.