Suggestion: An actual tags property in themes.json

[TheRealMG]

I'd like to suggest adding an actual tags property in themes.json so I can add better sorting on the theme store page on the site. It could be as simple as an array of strings users can add on theme creation or update, consisting of pre-approved tags.

This would help get rid of the somewhat archaic system currently used in the getThemesFromSearch() function on the site where the only real "tag" on the ZenTheme object is isColorTheme and everything else is just considered a "utility".

This is somewhat related to my previous suggestion #548 to add createdAt and updatedAt properties as well, to allow for better sorting and better user experience on the page.