MultisigAddress implementation

[syuan100]

• Create MultisigAddress from multiple Address objects

[mfalkvidd]

Thanks for looking into multisig support!

Adding cross-reference to
helium/HIP#157
and
helium/helium-wallet-rs#221

[syuan100]

@mfalkvidd I also saw that basic multisig functions have already been implemented in helium-crypto-rs: helium/helium-crypto-rs#21

Will be following this as a template

[syuan100]

Also, I raised this draft PR mostly for visibility so other people can jump on if necessary

[syuan100]

@mfalkvidd hello! I would like to have this reviewed for just the MultisigAddress implementation.

Another developer will be doing the rest of the multisig work. Thank you!

[syuan100]

Actually I just saw that there is a new "address" package. Should I move MultisigAddress into that package instead?

[syuan100]

Ok I just went ahead and refactored. Additionally, had to fix a test during merge if that's ok.

helium-js/packages/address/src/__tests__/Utils.spec.ts

Line 25 in 93c1276

const checksum = Buffer.from(bin.slice(-4))

[syuan100]

Closing in favor of #290