Document the `noirup` GitHub Action about docs HOT 3 CLOSED

I've included the github action in my merkle proof library: https://github.com/TomAFrench/noir-merkle/blob/master/.github/workflows/noir.yml

I've also got a version which is used in a repository with multiple noir projects as users will need to set the working directory to the project root: https://github.com/TomAFrench/noir-hashes/blob/master/.github/workflows/noir.yml

Edit: The lines below aren't necessary btw, I should probably remove them.

env:
  CARGO_TERM_COLOR: always

from docs.

@Globallager do you know if we are using this internally for testing in any of our public repos? That would be a good reference

from docs.

@Globallager do you know if we are using this internally for testing in any of our public repos? That would be a good reference

I don't think we're using it internally. @TomAFrench do share if you're aware of the GHA being used somewhere.

from docs.