Dark mode colour filter

[pete-w]

Please add white and secondary colours to the colour filter.

When creating drawings in light mode people tend to use black and primary colours to represent differing cuts (internal, external) and engraving (outline, filled) and it is great that LaserGRBL supports these:

• black
• red
• green
• blue

However when working in dark mode the usual colours are white and secondary:

• white
• cyan
• magenta
• yellow

Please add these addition colours to the colour filter so that designs generated in dark mode don't have to be re-coloured before importing.