Document usage on README.md

[benhylau]

First thing in the README.md should be step-by-step on how to use transports both from perspective of a user with "Free Basics" access, and how to run as an exit node to the real Internet. Some items that need to be clarified in the instructions:

Platform: Is Free Basics is only available to mobile phones? Then is transports?
Transports: WhatsApp, Facebook Messages, Free Basics (Are these all separate?)
Status: What transports work and what doesn't at the moment.
Criteria: For being able to take on a certain role.

I understand it's early stage of the project, but we can starting documenting the intended usage as we move.

[1Conan]

Here are some information that I know

Platform:
Free Basics website only works on mobile UA agents. But if you have use a simcard with access to Free Basics you can access it as long as you use a mobile UA agent.
Transports:
Free Basics isn't a transport. WhatsApp and Facebook Messages are the only transports.