Add `getBestBid` and `getBestAsk` functions to SDK

[metaproph3t]

I know how to get this from on-chain (just call bookside.best_price()), but I don't know how to do this from client

this would help a lot in surfacing prices to end-users

[mschneider]

hey @metaproph3t can you check if the new sdk works for you?

openbook-v2/ts/client/src/accounts/market.ts

Lines 160 to 162 in 9d7173a

	const bb = this.bids?.best();
	if (bb) {
	debug += ` best: ${bb.price} ${