Add some kind of doc/explanation about the 'Theme subfolder' option. #716
Description
What?
In the 'Edit theme metadata' modal, there's an option called 'Theme subfolder,' but it's not clear what it does or what to expect after changing it.
Expected
It should include at least some comment/doc explaining the behavior of this not obvious field.
Other fields in this modal have some explanations about their expected content. Example:
