Add note to docs about sign-off

Some "FAQs" and draft answers for discussion

How to sign-off a codelist?

• The codelist creator should save the codelist for review. It should be well-described so that reviewers know what is intended to be captured or excluded. A reviewer needs to create an account on OpenCodelists in order to sign off codelists. They should inspect the search terms used and the codes included excluded. They should comment on the related issue and/or contact the codelist creator to let them know they agree to sign it off.

Who should sign it off and how many people are enough?

• From main docs: Once a draft codelist has been agreed, we recommend it should be signed-off by at least two different people. (These can include the person who led on creating the codelist). This should usually include a "data expert" (epidemiological sign-off) and "disease expert" (clinical sign-off).

What does it mean to sign a codelist off?

• Sign-off indicates that the reviewer has inspected the search terms used and the codes included excluded, and they are happy from an epidemiological and/or clinical perspective that the codes will capture the condition/activity as intended.

What happens if a codelist is signed off, and is later updated?

• [Need to decide if this needs changing] Currently if a codelist is updated, the previous sign-offs are still present; the date of sign-off will indicate that it was prior to the current version release date.

Is sign-off mandatory?

• No. [should it be?]
• some options could be: not allow publication until sign-off (possibly not optimal because users can still use the codelist but it may not be publically visible?); display a "warning" message that the codelist is not signed off (with a link to these docs about what sign-off means).. anything else?
• Re updating codelists, we could similarly either prevent publication of new version without sign-off (this would involve linking sign-off to versions rather than codelists), or display a message that the current version is not signed off.

Start with the main docs and the FAQ draft in this issue; resolve the open decisions about updates and mandatory sign-off with maintainers before editing. Done means the agreed sign-off guidance is incorporated into the documentation, including what happens after updates and whether sign-off is required.