Colorize maps added by pwads in `listmaps` output

[yqco]

Adds color to `listmaps` command's output to highlight maps that are added or modified by pwads

listmaps-output.png

Personally, this helps to locate the maps I am most often using the listmaps command to find. Having the maps listed in a different color makes them much easier to spot.

This is kept as simple as possible. All highlighted maps use the same hard-coded TEXTCOLOR_LIGHTBLUE color

Pull request: https://github.com/ZDoom/gzdoom/pull/1941

[Professor Hastig]

Thanks for adding this. It is the kind of feature where you only realize what you missed after it got added.