Settings to invert colors of the images

Useful for novels, for reading in dark mode

src/lib/settings/settings.ts

@@ -57,6 +57,7 @@ export type Settings = {
   quickActions: boolean;
   fontSize: FontSize;
   zoomDefault: ZoomModes;
+  invertColors: boolean;
   volumeDefaults: VolumeDefaults;
   ankiConnectSettings: AnkiConnectSettings;
 };
@@ -84,6 +85,7 @@ const defaultSettings: Settings = {
   quickActions: true,
   fontSize: 'auto',
   zoomDefault: 'zoomFitToScreen',
+  invertColors: false,
   volumeDefaults: {
     singlePageView: false,
     rightToLeft: true,