[Docs] Update node.js docs to include .init() or .connect()

[BrettCleary]

The docs for node.js integration are missing this info

the issue happens because you are not initializing the sdk correctly.
Please check the examples folder or initialize the connection with the following:

const sdk = new MetaMaskSDK(options);
const accounts = await sdk.connect(); // or await sdk.init() then you can call eth_requestAccounts or any other methods.
The error you receive is because you are requesting an rpc method before the sdk has time to initialize and set the provider.

Reference
#409 (comment)
https://docs.metamask.io/wallet/how-to/connect/set-up-sdk/javascript/nodejs/

[christopherferreira9]

Hi @BrettCleary ! Docs are currently being updated and these instructions will be added.