Generate identicons from ETH address

[nya-elimu]

Add JavaScript function to the webapp for generating an identicon for a given ETH address.

We already have this implemented in a Node app: https://github.com/elimu-ai/web3-aragon-connect/blob/master/route/identicon/index.js

However, to reduce code complexity, we need to make this work in the Java webapp. We are already using web3.js in the webapp, so can web3.js be used for this purpose? If not, is there a way to port the existing Node solution to regular JavaScript?