message: Tweak sidebar background on macOS 11
  Inspired by Xcode, better fit on macOS 11 that tones down colors and
  grays a bit.
diff: @@ -168,6 +168,10 @@ wxColour ColorScheme::DoGet(Color color, Mode mode)
  // Backgrounds:
  case Color::SidebarBackground:
  + #ifdef __WXOSX__
  + if (@available(macOS 11.0, *))
  + return mode == Dark ? sRGB(46, 47, 50) : sRGB(240, 240, 240); // same as EditingThickSeparator
  + #endif
  return mode == Dark ? sRGB(45, 42, 41) : "#edf0f4";
  case Color::EditingBackground:
  