Enhance Localnet page

[rube-de]

As a new dev the pull instructions in the setup section would be helpful

docker pull ghcr.io/oasisprotocol/sapphire-localnet:latest

As a dev on apple sillicon it would be helpful to know how to pull the image with the platform param

docker pull ghcr.io/oasisprotocol/sapphire-localnet:latest --platform linux/x86_64

this is already in the info box at the bottom and could be combined.
It could be helpful for devs on apple silicon to have this info box directly after the normal command for better visibility