Add support for Anchor Events

[hjchan]

It is important to track historical data such as user past trades, daily fees, volume and etc.

[mzs-dev]

Need not be done programatically, can be fetched from historc data/logs from the client

[askibin]

protocols usually don't track historical data per user as it will require maintaining an ever-growing PDA. But let me know if you think something is missing in protocol-wide stats.

[hjchan]

ya, I think it shouldn't track historical using an ever-growing PDA but we should add anchor events, user trades for example, so protocols able to query the events easily and store them off-chain

[askibin]

yeah, that's not a bad idea, feel free to contribute!