[ltli] Add guidance to use `und` when unknown (#36)

aphillips has just created a new issue for https://github.com/w3c/ltli:

== Add guidance to use `und` when unknown ==
In two specs we've recently suggesting assigning `und` (rather than some other value) when the language tag is unknown. We need to document it here. We have similar text in specdev and string-meta

Please view or discuss this issue at https://github.com/w3c/ltli/issues/36 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Tuesday, 14 November 2023 21:15:35 UTC