Event design, especially with UX considerations across the signer provider ecosystem.

Attaching an `on` listener to `window.nostr` seems problematic, because `window.nostr` is not a persisted object, but an object injected by a specific provider. For example, when the user wants to switch or multisig signers and the i.e. `providerChanged` or `multisigUpdated` is emitted, `window.nostr` seems like an inappropriate place.

If we consider such case, is it better to only define the standard event name, and not where to listen?