Add warning for ref:REI=* values

[ivanbranco]

Description

ref:REI is a tag used in Italy for hiking relations, it has 13358 uses at the moment. As wiki, the value has to be of 8 characters, but sometimes people adds wrong values, with less or more characters. Would be possible for iD to warn the users about this problem?

At the moment there's a user doing gardening from time to time, but it would be cool if we could prevent this problem at the source, and use gardening time for other contributions. Thanks!

Screenshots

No response

[ankushKun]

Should be possible to show a warning for this by editing this innerWrap by adding a checker to .on("input")

I am working on this

[ankushKun]

Looked into the codebase a bit more and found a setup already exists for input validation. Added the REI value check as well

Sent a PR! #11656