Write a guide for adding support of a new blockchain

[GrayedFox]

Initial goal was to allow for easy exendability in terms of supporting diferebt blockchains and although it's certainly possible it's a bit more complex than my initial estimates.

• write a guide which explains the steps for adding a new blockchain (ideally: check their docs, map paths to local api commands like getTransactionByHash, then add default params where required)
• encourage users to make requests if they're happy to wait a little and don't want to touch the code