Generate a README.md file

It’s not immediately obvious what the different code club repos are for. This is apparent from the fact people often create issues against the static gh-pages repos (CodeClubUK-Projects and CodeClubWorld-Projects).

[x] It would therefore be useful for the CodeClubUK-Projects and CodeClubWorld-Projects repos to include README.md files, explaining that they are automatically generated, and just exist to serve the respective websites via Github Pages. It might even be useful to direct people to the curricula repos for filing issues.
[ ] ~~Once this is done, it would make sense to switch off issues for the CodeClubUK-Projects and CodeClubWorld-Projects repos:~~ UPDATE: The README is sufficient, and the issue trackers do come in handy. Let’s leave them on.

RaspberryPiFoundation / lesson_format

Generate a README.md file #39