Robonomics && Ledger devices

[tekken2028]

Currently, there is no support for Ledger devices, but I've heard it is quite easy to implement, and I think it is really relevant for a lot of XRT holders. Could you please add it?

[j0bberman]

Any news about Ledger support?

[akru]

Unfortunately Ledger support is still experimental for Polkadot projects, let me check it again.

@ensrationis @Fingerling42 It could be a good idea for a grant.

[KyojuHashira]

Have you guys implemented Ledger support?