fix(api.js): appWindow shown as type `any`, fixes #3747 (#3772)

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

.changes/appwindow-type-fix.md

@@ -0,0 +1,5 @@
+---
+"api": patch
+---
+
+Properly define the `appWindow` type.

tooling/api/rollup.config.js

@@ -53,7 +53,8 @@ export default [
       }),
       babel({
         configFile: false,
-        presets: [['@babel/preset-env'], ['@babel/preset-typescript']]
+        presets: [['@babel/preset-env'], ['@babel/preset-typescript']],
+        babelHelpers: 'bundled'
       }),
       terser()
     ],

tooling/api/src/window.ts

@@ -1168,7 +1168,7 @@ class WebviewWindow extends WindowManager {
 }
 
 /** The WebviewWindow for the current window. */
-let appWindow
+let appWindow: WebviewWindow
 if ('__TAURI_METADATA__' in window) {
   appWindow = new WebviewWindow(
     window.__TAURI_METADATA__.__currentWindow.label,