doc: Update README.md

jaywcjlove · jaywcjlove · commit 38a8f6ef491a · 2022-03-17T20:18:22.000+08:00
diff --git a/README.md b/README.md
@@ -142,15 +142,28 @@ Here is a simple footnote[^1]. With some additional text after it.
 
 ## Support dark-mode/night-mode
 
-By default, the `dark-mode` is automatically switched according to the system. If you need to switch manually, just set the `data-color-mode="dark"` parameter for body.
+By default, the [`dark-mode`](https://github.com/jaywcjlove/dark-mode/) is automatically switched according to the system. If you need to switch manually, just set the `data-color-mode="dark"` parameter for body. 
 
 ```html
-<body data-color-mode="dark"></body>
+<html data-color-mode="dark">
 ```
 
 ```js
-document.body.setAttribute('data-color-mode', 'dark')
-document.body.setAttribute('data-color-mode', 'light')
+document.documentElement.setAttribute('data-color-mode', 'dark')
+document.documentElement.setAttribute('data-color-mode', 'light')
+```
+
+Inherit custom color variables by adding [`.wmde-markdown-var`](https://github.com/uiwjs/react-markdown-preview/blob/a53be1e93fb1c2327649c4a6b084adb80679affa/src/styles/markdown.less#L1-L193) selector.
+
+```jsx
+const Demo = () => {
+  return (
+    <div>
+      <div className="wmde-markdown-var"> </div>
+      <MarkdownPreview source="Hello World!" />
+    </div>
+  )
+}
 ```
 
 ## Development
