Add example and docs

[linhbkhn95]

@0xsimulacra do u wann do it?

[0xsimulacra]

@linhbkhn95 I'm might work on it this week, but it is not promised.

I'm working against the clock to finish some parts of a golang sdk before my vacation in two weeks.

Thanks, and I'll see what I can do :).

[0xsimulacra]

I was only able to add thee usages examples on the ReadMe, one of them being an almost finshed version of UniswapV3 GetTickAtSqrtRatio wich use many methods of this package and another one is a Json Marshaling/UnMarshaling example.

Please take your time and give feedback on this last pull request:
#14

If you want me to make pull request of the usage examples alone, I can see if I can change them to use only the methods that existed before what I added on this pull request.