Add Quickstart README to Quickstart GB docs

[anettrolikova]

Hyperlane quickstart README has a lot of helpful commands on how to kickstart development on Hyperlane - this should be in Quickstart docs.

We should make Quickstart development page with commands to start with Hardhat and have the current page as quickstart overview = reference to other docs

Referring to: https://github.com/hyperlane-xyz/hyperlane-quickstart/ As well as: https://docs.hyperlane.xyz/docs/developers/quickstarts

[anettrolikova]

closing in favour of #1875

[nambrot]

Just seeing this now, i think the quickstart repo and the quickstarts on the docs do serve different purposes. I also quite like the quickstart repo, but i wouldn't say we should force everobody to use this over the docs