LibGUI: Add min_size to Layout

Author: https://github.com/frhun
Commit: b2951a2116
Pull-request: https://github.com/SerenityOS/serenity/pull/14261
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/MacDue
Reviewed-by: https://github.com/mjz19910

Userland/Libraries/LibGUI/Layout.h

@@ -12,6 +12,7 @@
 #include <LibCore/Object.h>
 #include <LibGUI/Forward.h>
 #include <LibGUI/Margins.h>
+#include <LibGUI/UIDimensions.h>
 #include <LibGfx/Forward.h>
 
 namespace Core {
@@ -49,6 +50,7 @@ public:
 
     virtual void run(Widget&) = 0;
     virtual Gfx::IntSize preferred_size() const = 0;
+    virtual UISize min_size() const = 0;
 
     void notify_adopted(Badge<Widget>, Widget&);
     void notify_disowned(Badge<Widget>, Widget&);