Expand examples to use and test all provided functions

[prusnak]

Currently, the examples/hwi.rs uses and tests only the functions related to enumeration of the devices (try_connect, device_kind, get_master_fingerprint, get_version).

It would be great if there was another example (maybe examples/sign.rs) which also tests functions related to signing (get_extended_pubkey , register_wallet , sign_tx ). This code should assume that the device is loaded with the standard SLIP-0014 mnemonic (12 * all). If this existed, it would be trivial to check whether implementation behaves correctly for new HW wallets (Trezor) being added to the project.

[pythcoiner]

i'm interested working on this