Dark Mode for wxPropertyGrid

see #18146, thanks to dkulp

src/propgrid/propgrid.cpp

@@ -1425,6 +1425,9 @@ void wxPropertyGrid::RegainColours()
         int colDec = -72;
     #endif
         wxColour capForeCol = wxPGAdjustColour(m_colCapBack,colDec,5000,5000,true);
+        if (wxPGGetColAvg(m_colCapBack) < 100)
+            capForeCol = wxSystemSettings::GetColour( wxSYS_COLOUR_WINDOWTEXT );
+        
         m_colCapFore = capForeCol;
         m_categoryDefaultCell.GetData()->SetFgCol(capForeCol);
     }