Account balances

[sohrab-]

SOL balances and token account balances should appear below an account (as part of the tags).

It would be great if token icons are dynamically downloaded (and memoised) and shown on screen. For now, we can have the details of the top 100 tokens hardcoded for this. Later to move to API.

Somethings to note:

• Amounts should update if there has been an airdrop or a network change
• Since the balances are affected by other external actors, we would need a refresh button on the balances as well.
• Need to be conscious of how chatty this is when there are a few accounts in the transaction, especially given that most public RPC endpoints are rate-limited
  • There could be a update cascade in some scenarios, such as changing the network
  • Should this be an option so users can turn off seeing the balances?
  • RPC endpoints allow batch requests. Does @solana/web3.js?