Replace JSX global with explicit ReactElement

Closes remarkjsGH-837.

Reviewed-by: Titus Wormer <[email protected]>

Author: remcohaszing

lib/index.js

@@ -1,6 +1,7 @@
 /**
  * @import {Element, ElementContent, Nodes, Parents, Root} from 'hast'
  * @import {Components as JsxRuntimeComponents} from 'hast-util-to-jsx-runtime'
+ * @import {ReactElement} from 'react'
  * @import {Options as RemarkRehypeOptions} from 'remark-rehype'
  * @import {BuildVisitor} from 'unist-util-visit'
  * @import {PluggableList} from 'unified'
@@ -134,7 +135,7 @@ const deprecations = [
  *
  * @param {Readonly<Options>} options
  *   Props.
- * @returns {JSX.Element}
+ * @returns {ReactElement}
  *   React element.
  */
 export function Markdown(options) {