sway/workspaces: sort by the "num" property provided by sway, configurable whether numeric workspace names come first

Sway provides the workspace "num" property which is an integer number of
the workspace, i.e., workspace "3" -> 3 and also "3dev" -> "3". This
commit uses this property to sort the workspaces, which makes sense when
persistent workspaces or all-output is specified. This commit also adds
a new configuration option, whether the numeric workspaces come in front
or after workspaces that have non-numeric name.

man/waybar-sway-workspaces.5.scd

@@ -64,6 +64,10 @@ Addressed by *sway/workspaces*
 	typeof: string ++
 	Command to execute when the module is updated.
 
+*numeric-first*: ++
+	typeof: bool ++
+	Whether to put workspaces starting with numbers before workspaces that do not start with a number.
+
 # FORMAT REPLACEMENTS
 
 *{value}*: Name of the workspace, as defined by sway.
@@ -107,6 +111,7 @@ n.b.: the list of outputs can be obtained from command line using *swaymsg -t ge
 "sway/workspaces": {
     "disable-scroll": true,
     "all-outputs": true,
+    "numeric-first": false,
     "format": "{name}: {icon}",
     "format-icons": {
         "1": "",