feat(window): add `incognito` option (#418)

Co-authored-by: Lucas Nogueira <lucas@tauri.studio>

.changes/window-incognito.md

@@ -0,0 +1,5 @@
+---
+"window-js": "minor"
+---
+
+Add `incognito` window configuration option

plugins/window/guest-js/index.ts

@@ -1884,6 +1884,14 @@ interface WindowOptions {
    * The user agent for the webview.
    */
   userAgent?: string;
+  /**
+   * Whether or not the webview should be launched in incognito mode.
+   *
+   * #### Platform-specific
+   *
+   * - **Android:** Unsupported.
+   */
+  incognito?: boolean;
 }
 
 function mapMonitor(m: Monitor | null): Monitor | null {