Interfaces to get color scheme details

[BLumia]

Make it possible for getting details of a color scheme like foreground and background color, actual color table and etc, by using the provided qtermwidget API. (feature request)

Expected Behavior

APIs for getting details of a color scheme like foreground and background color, actual color table and etc.

Current Behavior

No directly support for getting color table of a given color scheme, we can only get the list of color schemes, so developer can't make a color scheme preview without copy the qtermwidget color scheme file parser code to their project or write a new parser.

Possible Solution

Maybe make ColorScheme.h as a public library header?

Steps to Reproduce (for bugs)

1. check out qtermwidget.h.

Context

Would like to create a color scheme preview for my side project without copy and paste the color scheme parser code to the project.

System Information

• Distribution & Version: Debian (testing)
• Package version: 0.14.1-1