Deprecate the className prop

Users should wrap the `<Markdown>` component inside a `<div>` manually
instead.

Closes #781

changelog.md

@@ -2,6 +2,23 @@
 
 All notable changes will be documented in this file.
 
+## 9.0.1
+
+### Deprecate `className`
+
+The `className` prop was deprecated.
+Not only does the `className` prop add the `className` prop, it also implies a
+wrapper `<div>` will be created.
+Instead, you should wrap the content in a `<div>` manually.
+
+```jsx
+<div className={className}>
+  <Markdown>
+    {children}
+  </Markdown>
+</div>
+```
+
 ## 9.0.0 - 2023-09-27
 
 *   [`b67d714`](https://github.com/remarkjs/react-markdown/commit/b67d714)

lib/index.js

@@ -116,6 +116,7 @@ const deprecations = [
     id: 'replace-allownode-allowedtypes-and-disallowedtypes',
     to: 'allowedElements'
   },
+  {from: 'className', id: 'deprecate-classname'},
   {
     from: 'disallowedTypes',
     id: 'replace-allownode-allowedtypes-and-disallowedtypes',
@@ -266,8 +267,8 @@ export function Markdown(options) {
       let remove = allowedElements
         ? !allowedElements.includes(node.tagName)
         : disallowedElements
-        ? disallowedElements.includes(node.tagName)
-        : false
+          ? disallowedElements.includes(node.tagName)
+          : false
 
       if (!remove && allowElement && typeof index === 'number') {
         remove = !allowElement(node, index, parent)

readme.md

@@ -256,8 +256,6 @@ Configuration (TypeScript type).
     cannot combine w/ `disallowedElements`
 *   `children` (`string`, optional)
     — markdown
-*   `className` (`string`, optional)
-    — wrap in a `div` with this class name
 *   `components` ([`Components`][api-components], optional)
     — map tag names to components
 *   `disallowedElements` (`Array<string>`, default: `[]`)