add WAI-ARIA guideline to CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 94eb110ae54c24ea74ebf28a35b624f793a259ee..8f9bd3c44ad1b56cb5020826857dce39c91ffb71 100644 (file)
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -159,6 +159,7 @@ license your work under the terms of the [MIT License](LICENSE.md).
 - Always use proper indentation.
 - Use tags and elements appropriate for an HTML5 doctype (e.g., self-closing tags).
 - Use CDNs and HTTPS for third-party JS when possible. We don't use protocol-relative URLs in this case because they break when viewing the page locally via `file://`.
+- Use [WAI-ARIA](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA) attributes in documentation examples to promote accessibility.
 
 ### CSS