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>

electron-app/scripts/utils.js

@@ -0,0 +1,8 @@
+// @ts-check
+'use strict';
+
+// const isElectronPublish = false; // TODO: support auto-updates
+const isNightly = process.env.IS_NIGHTLY === 'true';
+const isRelease = process.env.IS_RELEASE === 'true';
+
+module.exports = { isNightly, isRelease };