Ad/yet more enhancement

[adonesky1]

• Makes the connect method asynchronous in the SDK and provider classes to handle race conditions and ensure proper connection before proceeding.
• Updates MetaMaskMultichainProvider to wait briefly after attempting to connect, allowing the onDisconnect event to fire if the connection fails, and checking the isConnected flag accordingly.
• Changes the invokeMethodResults data structure to store both the result and the request object.
• Moves SDK exports to a new index.ts file
• Adds a README.md for the SDK