docs(plugin-revealjs): improve docs

Author: Mister-Hope

docs/plugins/markdown/revealjs/README.md

@@ -110,6 +110,12 @@ You can enable the following themes in reveal.js via `themes` in plugin options:
 
 For the appearance of each theme, see [Themes demo](themes.md).
 
+::: important Assets Path
+
+Since markdown contents between `@slidestart` and `@slideend` are handled by Reveal.js at browser, so you can only use absolute paths for assets in slides, which must be accessible directly in browser, relative paths or alias are not supported.
+
+:::
+
 ## Slide Layout
 
 By default, the plugin registers a layout named `SlidePage` for you to render "a slides page".

docs/zh/plugins/markdown/revealjs/README.md

@@ -110,6 +110,12 @@ const add = (a, b) => {
 
 各主题的外观，详见 [幻灯片主题](themes.md)
 
+::: important 资源路径
+
+由于 `@slidestart` 和 `@slideend` 之间的 Markdown 内容由 Reveal.js 在浏览器中处理，因此你只能在幻灯片中使用绝对路径的资源，这些资源必须可以直接在浏览器中访问，不支持相对路径或别名。
+
+:::
+
 ## 幻灯片布局
 
 默认情况下，插件会注册一个 `SlidePage` 布局来供你渲染“幻灯片页”。