Explain user identity on EthVigil

[anomit]

Currently, EthVigil sets up a local wallet or uses a connected wallet from Metamask to use that Ethereum address as the definite identity for a user.

This has no relation to the Ethereum account address that sends out transactions from EthVigil. But it is a source of confusion for those who come from the prevalent paradigm of directly connecting to a dApp through a Metamask bridge.

Create a new section in the documentation section of Getting Started for this purpose.