Simplify HUD/VGUI2 Editing

[anewnick]

Editing BugfixedHL HUD/VGUI2 elements currently requires modifying TrackerScheme.res files or directly editing legacy sprite assets. This is technically demanding, requiring specific skills in .res file formats and familiarity with external image editors for sprites.

To make HUD customization significantly more accessible:

1. Allow replacing or modifying existing HUD graphics like .spr directly using modern graphical assets like PNG images, instead of relying solely on legacy sprites.
   This would enable users to edit visuals with graphic editing software, making it much easier for those without specialized sprite creation/editing skills.

2. Enhance the VGUI Editor:
   Develop a dedicated editor or tool within BugfixedHL specifically designed for creating and modifying HUD/VGUI2 elements, including support for modern graphical formats.
   This could involve tools like:
   A visual way to edit color schemes (color pickers) and fonts of VGUI2.
   An integrated sprite/image creation/editing panel using PNG/JPG import/export.