Request: Consider adding themes.json to main jar

[grimlock81]

This is a request. The flatlaf-demo.jar file contains a themes.json file under com\formdev\flatlaf\demo\intellijthemes

This file contains the list of all available FlatLAF themes (I assume it's all of them) as well as useful metadata about each theme including whether it's a dark theme or not. It would be useful to have this information available in the main flatlaf.jar file as I would like to offer the user the choice of which theme to use, and I would like to group the themes into Light Theme and Dark Theme groups.

Currently I get the list of available FlatLAF themes from the com.formdev.flatlaf.intellijthemes.FlatAllIJThemes.INFOS which only offers the name of the theme and not whether it's a dark theme or not.

Alternatively, is there a way of finding out whether a theme is dark or not without having to instantiate an instance of the ThemeLaf implementation. Thanks.

[DevCharly]

Don't want to ship themes.json because this may change in the future...

So I have added the dark flag to FlatAllIJThemes.INFOS in recent commit.