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

.gitignore

@@ -1,5 +1,6 @@
 node_modules
 auth_info*.json
+baileys_store*.json
 output.csv
 */.DS_Store
 .DS_Store