Rework the readme to outline basic usage and value prop

[nirinchev]

I think our Readme should cover the value proposition of Realm and give a few examples of how it's used rather than link to a bunch of different places. As a new user, it's going to be hard to understand what the project is about without investing a lot of time following the different links.

[sync-by-unito]

➤ papafe commented:

For now I removed myself from the assignee. I think we need to revisit this together with the renaming, and eventually in sync with other teams too.