Vamp up the README

[frankiebee]

closes #443
The purpose of this PR is to "kick off" better docs and to get one step closer to getting our docs up on the docs website:

What the README has now:

• Quick overview (what this SDK is for, who it's for, some example use-cases)
• Installation instructions
• Basic usage example (bonus: runnable code)
• Links to detailed docs over at docs.entropy.xyz (@johnnymatthews this one is on you)

BONUS:

• test for the code example (if this ever fails the readme needs to be updated!)

[frankiebee]

🔥 HEADS UP: you'll see i've added a test here: tests/README.test.ts 😈 it parses the README for the code example. this does mean the read me is now a sensitive place however it also means that if you change the api surface and dont update the read me to match the executable it will fail the tests! 🔥

[johnnymatthews]

@frankiebee are you done with this PR? If so, I'd like to run through it before it gets merged. Don't wanna step on your toes if you're still working on it though.

[frankiebee]

@frankiebee are you done with this PR? If so, I'd like to run through it before it gets merged. Don't wanna step on your toes if you're still working on it though.

i'm done writing doc words so please take a look! i would like you too
dont worry about stepping on my feet they are very strong