feat: implement in memory store

1. the store works as a temporary store for connection data such as chats, messages & contacts
2. the store is primarily meant to illustrate the usage of the event emitter as a way to construct the state of the connection. This will likely be very inefficient to perform well at scale
3. the store is meant to be a quick way to have some visibility of data while testing
4. the store works for both legacy & MD connections

src/index.ts

@@ -4,7 +4,7 @@ import makeWASocket from './Socket'
 export * from '../WAProto'
 export * from './Utils'
 export * from './Types'
-//export * from './Store'
+export * from './Store'
 export * from './Defaults'
 export * from './WABinary'