Update README with endpoints for the different wallet address used in the project

[Larry8668]

Mention the some of the different endpoint that are being used

Also add reference to the backend-repo https://github.com/pramaths/onchainanalysis in the README

(⚠️ Do not update anything else, just add anything that seems relevant and is missing currently)

[aparna-u]

Hi, I would like to take on this issue, Please assign this issue to me.

[Larry8668]

@aparna-u Sure, good luck.