Update the README.md for Tool chain installation

Created by: Sanket-0510

This issue is for improvement in the tool chain installation guide for new comers. sudo $WALLY/bin/wally-tool-chain-install.sh triggers all the installation command at the same time this can cause system to run out of memory eventually crashing down, atleast my system crashed and stopped all the running processes. We can break down the https://github.com/openhwgroup/cvw/blob/main/bin/wally-tool-chain-install.sh file in steps for the installation guide.