Document API reference for @chainlink/ea-bootstrap and @chainlink/types

[aelmanaa]

Hello,

I was thinking of re-writing this guide Building external adapters by following the Contributing section and generating an adapter from scratch using yarn new source <adapter-name>.
Unfortunately, I have to do some reverse engineering since @chainlink/ea-bootstrap and @chainlink/types don't have API references (I have to read every imported object and try to understand what it does). Probably other people will run into the same issue. Hence was thinking that we should document every class & function and then generate API references.

I can help with that if you want