Improve readme information
At the moment, the main README file in the repository is just one sentence. It would be nice to make this look a bit nicer and more complete. I don't think it's the place to put any concrete documentation, but we can provide a number of useful links. The main idea is to make it easier for newcomers (or people unfamiliar with the system) to find all the different resources and get a quick idea of what CTA is; the idea is not to repeat a bunch of information from the official docs.
I would propose to do this after the documentation overhaul (#694) so that we can nicely refer to a few specific links as well (e.g. how to build, operator tools, design, etc.).