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/vite.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from 'vite'
+
+export default defineConfig({
+  optimizeDeps: {
+    include: ['flexsearch']
+  },
+  build: {
+    target: 'es2019',
+    cssCodeSplit: true,
+    sourcemap: false,
+    chunkSizeWarningLimit: 1200
+  }
+})
+