feat: 添加图标和路由配置

- 新增多个 SVG 图标文件
- 添加 `/demo/icons` 路由配置，用于图标预览

src/assets/svg/xt-face-frown-fill.svg

@@ -0,0 +1,3 @@
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M12 22C17.5228 22 22 17.5228 22 12C22 6.47715 17.5228 2 12 2C6.47715 2 2 6.47715 2 12C2 17.5228 6.47715 22 12 22ZM8 8.5V11.5H10V8.5H8ZM14 11.5V8.5H16V11.5H14ZM9.21802 17.3745C9.3639 17.0133 9.58343 16.674 9.87868 16.3787C11.0503 15.2071 12.9497 15.2071 14.1213 16.3787C14.4166 16.674 14.6361 17.0133 14.782 17.3745L16.6364 16.6255C16.3918 16.0198 16.0241 15.4531 15.5355 14.9645C13.5829 13.0119 10.4171 13.0119 8.46447 14.9645C7.97585 15.4531 7.60819 16.0198 7.36355 16.6255L9.21802 17.3745Z" fill="currentColor"/>
+</svg>