Explicitly set detail popover text fg color

The main window environment seems to be preserved
on macOS Catalyst (preserving the "white" color
of the main window).

Sources/5GUIs/Views/Windows/MainWindow/DetailsPopover.swift

@@ -37,6 +37,7 @@ struct DetailsPopover: View {
           }
         }
       }
+      .foregroundColor(Color(NSColor.textColor))
     }
   }