Fix typo in html! concept docs (#3096)

I am learning Yew and noticed this small typo in the docs as I was reading through it, so I thought I'd fix it :)

Author: lukependleton

website/versioned_docs/version-0.20/concepts/basic-web-technologies/html.mdx

@@ -39,7 +39,7 @@ let combined_html: Html = html! {
 };
 ```
 
-One rule major rule comes with use of `html!` - you can only return 1 wrapping node.
+One major rule comes with the use of `html!` - you can only return 1 wrapping node.
 To render a list of multiple elements, `html!` allows fragments. Fragments are tags
 without a name, that produce no html element by themselves.