feat: add ContextBridgeMutability feature (#27348)

spec-main/fixtures/api/context-bridge/context-bridge-mutability/main.js

@@ -0,0 +1,20 @@
+const { app, BrowserWindow } = require('electron');
+const path = require('path');
+
+let win;
+app.whenReady().then(function () {
+  win = new BrowserWindow({
+    webPreferences: {
+      contextIsolation: true,
+      preload: path.join(__dirname, 'preload.js')
+    }
+  });
+
+  win.loadFile('index.html');
+
+  win.webContents.on('console-message', (event, level, message) => {
+    console.log(message);
+  });
+
+  win.webContents.on('did-finish-load', () => app.quit());
+});