Review and update README

[DavidBiddle]

Issue #984 raised a possible problem with out of date content in the 'Additional commands for Apple silicon' section of the README.md. We aren't sure whether the is particular section is still relevant, and most of the content on the page is more than a year old so it's likely due a review anyway.

We should review it to make sure:

• instructions for running locally are still relevant
• links are still up to date (since the link checker doesn't run on this doc as it does for the actual GDS Way pages)
• any other content still makes sense
• check whether the openssl issue in Requirement for openssl@1.1 needs to be updated #984 needs resolving