Add tags to other tags (a tree of tags)

[TheOriginalSoni]

Basically a way to put tags in other tags (so basically a tag-tree).

Or alternatively, add tags to tags.

For example, the tag compounding would be marked with allomancy and feruchemy both. So if you search for compounding, you get everything marked with compounding. But if you search for allomancy, you get everything marked with compounding as well as allomancy

Similar to how Categories in Wikis behave