Added settings for misc. & tools preferences with fullscreen option

src/lib/extension/settings/MiscSettings.js

@@ -0,0 +1,32 @@
+import CacheableSettings from "$lib/extension/base/CacheableSettings.js";
+
+export default class MiscSettings extends CacheableSettings {
+  constructor() {
+    super("misc");
+  }
+
+  async resolveFullscreenViewerEnabled() {
+    return this._resolveSetting("fullscreenViewer", false);
+  }
+
+  async setFullscreenViewerEnabled(isEnabled) {
+    return this._writeSetting("fullscreenViewer", isEnabled);
+  }
+
+  /**
+   * @param {function(MiscSettingsObject): void} callback
+   * @return {function(): void}
+   */
+  subscribe(callback) {
+    return super.subscribe(settings => {
+      callback({
+        fullscreenViewer: settings.fullscreenViewer ?? false,
+      })
+    });
+  }
+}
+
+/**
+ * @typedef {Object} MiscSettingsObject
+ * @property {boolean} fullscreenViewer
+ */