View RPC method request: New transaction detected

[grod220]

Related to: https://github.com/penumbra-zone/web/issues/80

We'd like to build a feature where the web app triggers a toast notification when a new note is detected (to the user, symbolizing an incoming transaction, successful swap, etc). This requires a new view rpc streaming method. One that subscribes to the notes table and emits an event on additions. Perhaps swaps table too? 🤔

[hdevalence]

Rather than watching the notes table and returning notes, maybe it would be more generally useful to watch the transactions table and return TransactionInfo?