Add names and links of the various sub-repos

Lots of work is being done, towards making `py-ipfs` a complete project.
However, since the dependencies and all need to be worked up from scratch, not much work is being done directly in this repo. Various contributors are working on various other repos.
Maybe, we can put a link to those repos in the `README.md` file, so that new contributors know where to look for issues and where to contribute.
1 more suggestion: We can separate those repos as:
1. Core jobs (The protocols ...)
2. Dependencies (libp2p ...)

Start with README.md and identify the related repositories referenced by the py-ipfs project. Organize their names and links under the suggested Core jobs and Dependencies categories, or clarify the categories if the repository list does not fit them. Done means new contributors can find where to look for issues and contribute.

Written by the indexing model from the issue text.