fix(xworkspace): Fully support _NET_DESKTOP_NAMES spec (#1579)

Ref https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#idm140200472706208

Fixes #1491
Fixes #248
Closes #904

include/modules/xworkspaces.hpp

@@ -69,6 +69,7 @@ namespace modules {
     void set_desktop_urgent(xcb_window_t window);
 
     bool input(string&& cmd);
+    vector<string> get_desktop_names();
 
    private:
     static constexpr const char* DEFAULT_ICON{"icon-default"};