document how to create a new key type and add it to the keyring

[fedekunze]

Summary

• document how to create a new key type and add it to the keyring

Problem Definition

Currently, the process of adding a new key type (eg: The Eth's secp256k1 used on Ethermint) to the keyring in not fully documented/tested, and it would be extremely helpful to add a dev guide.

Proposal

• Add a document/guide to add and register a new key type to the keyring that's used for custom account types
• Ideally, test the guide with a custom key type/algorithm. Currently, we only have a test for a not supported algorithm option (notSupportedAlgo) that uses the same default hd.Secp256k1 type. This will prevent issues like client/keys: --algo flag silently falls back to default if user supplied algo is not supported #6402 from happening again.

cc: @alessio @jgimeno

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[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jgimeno]

docs/basics/accounts.md has to be updated too, I think the Keybase api changed a little since then.