4 Readme Changes

[Thovthe]

Added:
A table of contents
A community software section that should allow closing Issue #8
A statement of general licensing intent

The diff looks a little weird at the bottom but I just formatted the name of RaspberryPi

[danjulio]

Thanks for the suggestions. I have the following comments, questions about this PR.

1. I'm not sure why that page needs a TOC. I don't see that it adds anything to navigation. Perhaps just additional wording in the first paragraph indicating the repository contains code and designs for the various platforms I have experimented with (honestly I should have split this into a bunch of repositories but don't want to know because of all the links pointing here).
2. For the licensing section I think I'd rather say that there are a variety of licenses in use, including "as-is" and perhaps a note that some licenses are TBD.
3. We should be explicit that the R-package relates to the ESP32 directory.