Suggestion: Add section to describe wallets that can support web3 mnemonics (BIP39, BIP32, BIP44)

[ehanoc]

The arch document sections related to key management and wallet features, only speak on hardware vs software mode. I think there's a path missing that we should describe that wallets could support when self-custody of keys is a requirement (i.e blockchain based systems, self-sovereign identity) , which is when the user brings their own keys.

There's also a scenario where external hardware might be used (i.e Ledger, Trezor).

I'm open to make a proposal to the docs to describe this if it would be considered.

Thank you!