[Feat]: Add an option for "deprecation warning" for a value

[assapir]

I wish there were a way to set a deprecation warning in the table, which will automatically add the warning on the value to warn the users. Maybe something like @deprecated - this is deprecated because..., which will cause the table to have a line with this warning before this value. If that applies to a section with sub-values, it will also be added to all the sub-values.

[norwoodj]

I think this is not a bad idea, the trick will be displaying it in a reasonable way. Happy to look at a PR.