Clarifying how to apply aria-* attributes (#9843)

Provide explicit example of what "keep lowercase" means for `aria-*` attributes.

docs/reference-dom-elements.md

@@ -16,7 +16,7 @@ redirect_from:
 
 React implements a browser-independent DOM system for performance and cross-browser compatibility. We took the opportunity to clean up a few rough edges in browser DOM implementations.
 
-In React, all DOM properties and attributes (including event handlers) should be camelCased. For example, the HTML attribute `tabindex` corresponds to the attribute `tabIndex` in React. The exception is `aria-*` and `data-*` attributes, which should be lowercased.
+In React, all DOM properties and attributes (including event handlers) should be camelCased. For example, the HTML attribute `tabindex` corresponds to the attribute `tabIndex` in React. The exception is `aria-*` and `data-*` attributes, which should be lowercased. For example, you can keep `aria-label` as `aria-label`.
 
 ## Differences In Attributes