chore(deps): Updated to Theia 1.39.0 (#2144)

- update Theia to `1.39.0`,
 - remove the application packager and fix the security vulnerabilities,
 - bundle the backed application with `webpack`, and
 - enhance the developer docs.

Co-authored-by: Akos Kitta <a.kitta@arduino.cc>
Co-authored-by: per1234 <accounts@perglass.com>

Signed-off-by: Akos Kitta <a.kitta@arduino.cc>

arduino-ide-extension/src/browser/widgets/sketchbook/create-new.tsx

@@ -1,4 +1,4 @@
-import * as React from '@theia/core/shared/react';
+import React from '@theia/core/shared/react';
 
 export class CreateNew extends React.Component<CreateNew.Props> {
   override render(): React.ReactNode {

arduino-ide-extension/src/browser/widgets/sketchbook/sketchbook-composite-widget.tsx

@@ -1,4 +1,4 @@
-import * as React from '@theia/core/shared/react';
+import React from '@theia/core/shared/react';
 import { createRoot, Root } from '@theia/core/shared/react-dom/client';
 import { inject, injectable } from '@theia/core/shared/inversify';
 import { nls } from '@theia/core/lib/common/nls';

arduino-ide-extension/src/browser/widgets/sketchbook/sketchbook-tree-widget.tsx

@@ -1,4 +1,4 @@
-import * as React from '@theia/core/shared/react';
+import React from '@theia/core/shared/react';
 import {
   inject,
   injectable,
@@ -62,12 +62,16 @@ export class SketchbookTreeWidget extends FileTreeWidget {
   }
 
   @postConstruct()
-  protected override async init(): Promise<void> {
+  protected override init(): void {
     super.init();
     // cache the current open sketch uri
-    const currentSketch = await this.sketchServiceClient.currentSketch();
-    this.currentSketchUri =
-      (CurrentSketch.isValid(currentSketch) && currentSketch.uri) || '';
+    this.sketchServiceClient
+      .currentSketch()
+      .then(
+        (currentSketch) =>
+          (this.currentSketchUri =
+            (CurrentSketch.isValid(currentSketch) && currentSketch.uri) || '')
+      );
   }
 
   protected override createNodeClassNames(