new libraries required

## Abstract

### BIP32

I see 2 options:

* [bip32 from trezor](https://github.com/trezor/trezor-crypto/blob/master/bip32.c): this would need to be cleaned up (of altcoin code), it has many dependencies, including secp256k1 (written by trezor). It would probably need tweaking to work on arduino.

* there is a library [Micro-Bitcoin](https://github.com/micro-bitcoin/uBitcoin) by stepan snigirev which is also based on trezor crypto. But this library already works out of the box on arduino. It also supports psbts, different types of address derivation etc. It is nice to work with.

### QR encoded UR format

From bc-seedtool-cli the following is required:
* cbor
* ur
* bc-bech32

I will rewrite this (or the necessary subset of it) for Arduino.

## Questions

What are your thoughts on bip32 library? I'm thinking second option.