Implement /search

There should be a command to search a given word in all the past messages.

Feature: “/search [searched-word]”

Command : /search

Usage : [searched-word]

Functionality: In all kinds of conversation tabs

Description: This feature will search for a message in the past based on the “searched-word”. The output would be an automatic scroll to the message related to the “searched-word” and highlighting that word of the message.