Palette QOL changes

[Variable-ind]

I noticed some aspects of the palette panel were in need of improvement so this PR addresses these

• Clicking a swatch with Left/Right color now directly add the color to the desired swatch. This saves the trouble of re-arranging the swatch (if required) to the desired place each time a new color is added
• Previously when deleting a color from palette, you'd have to select color and then press delete button. This is fine for removing one or two colors but when removing a chunk of colors, this task becomes cumbersome. You can now remove colors by Ctrl + click on the desired swatch.

Before

demo-.5.mp4

After

demo-.6.mp4

• A new Auto add colors option has been made available. When enabled, NEW colors drawn on canvas will automatically get added to the palette if space is available. (This does not remove colors)

[OverloadedOrama]

Looks good, thank you!