Allow extension register custom topbar menu command (#982)

* Refactor command store

* Rename coreMenuStore to menuStore

* Extension API to register command

* Update README

* Add playwright test

browser_tests/extensionAPI.spec.ts

@@ -0,0 +1,32 @@
+import { expect } from '@playwright/test'
+import { comfyPageFixture as test } from './ComfyPage'
+
+test.describe('Topbar commands', () => {
+  test.beforeEach(async ({ comfyPage }) => {
+    await comfyPage.setSetting('Comfy.UseNewMenu', 'Floating')
+  })
+
+  test.afterEach(async ({ comfyPage }) => {
+    await comfyPage.setSetting('Comfy.UseNewMenu', 'Disabled')
+  })
+
+  test('Should allow registering topbar commands', async ({ comfyPage }) => {
+    await comfyPage.page.evaluate(() => {
+      window['app'].extensionManager.menu.registerTopbarCommands(
+        ['ext'],
+        [
+          {
+            id: 'foo',
+            label: 'foo',
+            function: () => {
+              window['foo'] = true
+            }
+          }
+        ]
+      )
+    })
+
+    await comfyPage.menu.topbar.triggerTopbarCommand(['ext', 'foo'])
+    expect(await comfyPage.page.evaluate(() => window['foo'])).toBe(true)
+  })
+})