Support D2ExpRes.ini config format (or similar)

[IAmTrial]

D2ExpRes is a popular choice for resolution customization in Diablo II version 1.10. The level of customization allows modders to control most, if not all, graphical display elements.

This feature should be entirely optional. It should only activate if a config option is set to true. The customizability options should be a part of the JSON config option. If the config option is set to false, then the software should behave similar to before. The customization entries don't need to be the same entries as those provided by D2ExpRes.ini. They can have entirely different names, some entries could be removed, and new entries could be added.

This feature is necessary for modders who depend on D2ExpRes features, and would significantly improve the customizability of mods based on other versions of Diablo II.