docs: add VitePress documentation site

- Add docs directory with VitePress configuration
- Add GitHub Actions workflow for docs build and deploy
- Support bilingual (English/Chinese) documentation
- Include search, custom theme, and responsive design

docs/.vitepress/theme/index.ts

@@ -0,0 +1,25 @@
+import DefaultTheme from 'vitepress/theme'
+import ThemeSwitcher from './components/ThemeSwitcher.vue'
+import DocSearch from './components/DocSearch.vue'
+import DarkModeToggle from './components/DarkModeToggle.vue'
+import CopyCodeButton from './components/CopyCodeButton.vue'
+import Breadcrumb from './components/Breadcrumb.vue'
+import PageToc from './components/PageToc.vue'
+import Layout from './layouts/Layout.vue'
+import './styles/variables.css'
+import './styles/custom.css'
+import './styles/mobile.css'
+
+export default {
+  extends: DefaultTheme,
+  Layout,
+  enhanceApp({ app, router, siteData }) {
+    // Register global components
+    app.component('ThemeSwitcher', ThemeSwitcher)
+    app.component('DocSearch', DocSearch)
+    app.component('DarkModeToggle', DarkModeToggle)
+    app.component('CopyCodeButton', CopyCodeButton)
+    app.component('Breadcrumb', Breadcrumb)
+    app.component('PageToc', PageToc)
+  }
+}