Add some color modes: Invert Lightness/Luma, Hue Shift

This adds some new Render Modes:

• Invert Lightness: As a night mode for documents with colorful text markup. Black and white are inverted, but saturated colors are not affected.
• Invert Luma: As a night mode for documents with images or graphics. Black and white are inverted, but contrast in some images is better preserved than with Invert Lightness.
• Invert Luma Symmetric: One more night mode, between Invert Lightness and Invert Luma. For documents with both colorful text markup and images.
• Hue Shift Positive/Negative: Converts red to green, green to blue, etc; black and white are not affected. This could be helpful for color blind people, because they can shift some graphics into their individual color space. But I’m not an expert on this topic. Anyway, it can be helpful for people with normal vision, as it can mitigate some low contrast conditions.

Configuration window:

Normal colors (already existing, of course):

Invert Colors (already existing): Note that it looks fine, but the image is heavily changed.

Invert Lightness:

Invert Luma:

Invert Luma Symmetric: Very similar to Invert Lightness, but some letters are better readable.

Hue Shift 120°:

Hue Shift 240°:

~"Visual Design Group"