Implement new package with multichain demo frontend app

[esaminu]

Description

• Deploy to vercel
• Hardcode an account with a FAK locally first to get it working with signMultichain then in future use fastauth sign in and create account
• Once signed in, use multichain account id value from config (possibly env) to fetch the root key and derive accounts for in canonical JSON per https://github.com/near/near-fastauth-wallet/blob/dmd/chain_sig_docs/docs/chain_signature_api.org#serialization-format:
  - {"chain": 0, "domain": "near.org"}
  - {"chain": 0}
  - {"chain": 60, "domain": "near.org"}
  - {"chain": 60}
• Allow users to select the type of key from a dropdown in the detail page
• Implement second route for the detail with an amount and "Send" button which calls near-fastauth-wallet signMultichain method Implement new signMultiChain method near-fastauth-wallet#17

[firatNEAR]

Forgive my ignorance, are we expecting the user to select which key they want to use or does the app suggest a key that works for their specific domain?

[esaminu]

For this demo app the user will be able to select which key they'd like to use after they select the asset. We will give them a drop down to select either the domain key or their personal key