Added dialog with shortcuts to the SLA gizmo, tried to improve the dialog look

src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp

@@ -11,6 +11,7 @@
 
 #include "libslic3r/SLA/SLACommon.hpp"
 #include "libslic3r/SLAPrint.hpp"
+#include <wx/dialog.h>
 
 
 namespace Slic3r {
@@ -139,6 +140,12 @@ protected:
 };
 
 
+class SlaGizmoHelpDialog : public wxDialog
+{
+public:
+    SlaGizmoHelpDialog();
+};
+
 } // namespace GUI
 } // namespace Slic3r