Make ribbon tab active/hover label colour customizable

Allow changing the colour of the label in the active and hover states to
make it possible to improve its contrast with the tab background in
these states.

Closes #18406.

interface/wx/ribbon/art.h

@@ -66,6 +66,10 @@ enum wxRibbonArtSetting
     wxRIBBON_ART_GALLERY_BUTTON_DISABLED_FACE_COLOUR,
     wxRIBBON_ART_GALLERY_ITEM_BORDER_COLOUR,
     wxRIBBON_ART_TAB_LABEL_COLOUR,
+    /// @since 3.1.3
+    wxRIBBON_ART_TAB_ACTIVE_LABEL_COLOUR,
+    /// @since 3.1.3
+    wxRIBBON_ART_TAB_HOVER_LABEL_COLOUR,
     wxRIBBON_ART_TAB_SEPARATOR_COLOUR,
     wxRIBBON_ART_TAB_SEPARATOR_GRADIENT_COLOUR,
     wxRIBBON_ART_TAB_CTRL_BACKGROUND_COLOUR,