[feature] Add env var to show/hide Chat History Button

[iseabock]

Motivation and Context

Many of the UI element are customizable now so I have added Show Chat History to that list.

Description

Contribution Checklist

• [x] I have built and tested the code locally and in a deployed app
• [x] For frontend changes, I have pulled the latest code from main, built the frontend, and committed all static files.
• [x] This is a change for all users of this app. No code or asset is specific to my use case or my organization.
• [x] I didn't break any existing functionality :smile:

[kagoolastha23]

This branch when executed gave me Application Error. Any idea how to resolve it?