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/arduino-ide-electron-main.js

@@ -0,0 +1,25 @@
+// @ts-check
+'use strict';
+
+const os = require('os');
+const path = require('path');
+const config = require('./package.json').theia.frontend.config;
+// `buildDate` is only available in the bundled application.
+if (config.buildDate) {
+  // `plugins` folder inside IDE2. IDE2 is shipped with these VS Code extensions. Such as cortex-debug, vscode-cpp, and translations.
+  process.env.THEIA_DEFAULT_PLUGINS = `local-dir:${path.resolve(
+    __dirname,
+    'plugins'
+  )}`;
+  // `plugins` folder inside the `~/.arduinoIDE` folder. This is for manually installed VS Code extensions. For example, custom themes.
+  process.env.THEIA_PLUGINS = [
+    process.env.THEIA_PLUGINS,
+    `local-dir:${path.resolve(os.homedir(), '.arduinoIDE', 'plugins')}`,
+  ]
+    .filter(Boolean)
+    .join(',');
+  // Enables the file logger in the backend process.
+  process.env.IDE2_FILE_LOGGER = 'true';
+}
+
+require('./lib/backend/electron-main');