feat: Added methods to handle new transactions

[jinoosss]

Description

This PR adds RPC feature support for new transactional events.

This is what works for this PR.

• Adds a newTransactionFilter method and creates a filter.
• Check for changes to the transaction filter with the existing getFilterChanges method.
• Subscribe to transaction creation events via the newTransactions parameter of the websocket subscribe method.

Examples

Using Transaction filter to get transactional changes

Subscribe to transaction events with websockets

[jinoosss]

Could you give me some feedback on supporting RPC functionality for transactional events?

[zivkovicmilos]

Thank you for adding this missing functionality 🙏

I've left a few comments that should be addressed before merging this out. My primary concern is emitting an event in the fetcher for new txs, when we already emit a block event that contains the txs -> I think we should just stick to the block event, and in the FM construct individual tx events for the tx listeners

Tx filters aren't applied because Apply is never called (the apply logic should happen in UpdateWith). We're also missing handling tx filter options when the user creates a transaction filter

I think we're 80% there, these few things are the blockers 🙏

[ajnavarro]

Not a fan of our actual memory filters, created an issue (#38) to improve them.

They might not be even needed, the events JSON RPC API is using WebSockets, right? So we know when a client disconnects, so we might do the same we are doing on GraphQL API.

[jinoosss]

They might not be even needed, the events JSON RPC API is using WebSockets, right? So we know when a client disconnects, so we might do the same we are doing on GraphQL API.

Yes, it can work like GraphQL's subscription feature.
For now, GraphQL's filter feature works better.

But it's also nice to provide familiar and accessible functionality.
The specification for JSON RPC is familiar to users.

[zivkovicmilos]

Thank you for fixing this up 🙏

I apologize for the late reply on this, looks great now 💯