Add derivation path for wallet-config

[friedger]

[MichaelFedora]

Hey @friedger , how does this differ from #9 ? I haven't been keeping up with stacks these days and am still using blockstack.js in my code so I'm not sure how/where this could be done simply.

[friedger]

@MichaelFedora the wallet config is a special derivation path for each account, similar to the stack derivation path and the data derivation path or a app key derivation path.

[MichaelFedora]

Why would a file browser need to know the wallet address of an account?