Update CLI scaffolded README

[technophile-04]

Description :

Currently, after scaffolding project through CLI the monorepo README always shows hardhat instruction due to :

https://github.com/scaffold-eth/scaffold-eth-2/blob/cli/templates/base/README.md

We can tackle this with two approaches :

Simple :

• Update templates/base/README.md such that it contains both hardhat and foundry instruction checkout https://docs.scaffoldeth.io/quick-start/environment

Better approach:

• We can create separate README's for both one in templates/extensions/hardhat for hardhat and second inside templates/extensions/foundry with their respective instruction.

Second approach make more sense to me since when

[carletex]

I like the second one better too!

[technophile-04]

Completed in #782