Feature: Add tag meta classes

[dgkf]

Since it can be tedious to set the same linters for many things that you probably want to behave similarly, it might be nice to have linters for collections, eg

"value_descriptions": A set of @param descriptions and @return descriptions
"headers": A set of @title and any section sub-titles

This would need some extra handling for registration so that roxytypes can register into the "value_descriptions" meta class and include a @typed param description.