resources/images: Add $image.Colors

Which returns the most dominant colors of an image using a simple histogram method.

Fixes #10307

resources/images/color.go

@@ -45,6 +45,14 @@ func ReplaceColorInPalette(c color.Color, p color.Palette) {
 	p[p.Index(c)] = c
 }
 
+// ColorToHexString converts a color to a hex string.
+func ColorToHexString(c color.Color) string {
+	r, g, b, a := c.RGBA()
+	rgba := color.RGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
+	return fmt.Sprintf("#%.2x%.2x%.2x", rgba.R, rgba.G, rgba.B)
+
+}
+
 func hexStringToColor(s string) (color.Color, error) {
 	s = strings.TrimPrefix(s, "#")