Limit Order Book Demo

- algo theory from https://github.com/Kautenja/limit-order-book/blob/master/notes/lob.md
- AVL tree impl from https://github.com/bitmark-inc/bitmarkd/tree/master/avl
- worst op complexity O(2log n)
- scaling up: sharding the trees 

Running

go mod tidy
go run main.go