Fix #4919: Create Swatch Legend

swatch.legend draws a grid of chips, one per colour swatch (the given
ones, else every one), each filled with and linked to its swatch and
labelled with its name and colour values (HEX, RGB, CMYK, Lab or
Grayscale; by default its own model; spot swatches marked), black on
light chips and white on dark ones, as one selected group in one undo
step. The Swatches panel menu's Create Swatch Legend draws the selected
colour swatches, else every one.

crates/engine/src/cmd.rs

@@ -84,6 +84,7 @@ mod stroke;
 mod style;
 pub mod stylelib;
 mod swatch;
+pub mod swatchlegend;
 pub mod swatchlib;
 pub(crate) mod symboledit;
 pub mod symbollib;
@@ -297,6 +298,7 @@ pub fn command_specs() -> &'static [CommandSpec] {
         v.extend(paint::proxy_specs());
         v.extend(overprint::specs());
         v.extend(swatchlib::specs());
+        v.extend(swatchlegend::specs());
         v.extend(freeform::specs());
         v.extend(flatten::specs());
         v.extend(stylelib::specs());