feat(YouTube): Adds documentation for YouTube options

Author: seanmcn

README.md

@@ -748,6 +748,15 @@ https://youtu.be/dQw4w9WgXcQ
 
 </details>
 
+#### Options
+
+All options should go under the `YouTube` namespace.
+
+| name   | Type     | Required | Default | Description                  |
+| :----- | :------- | :------- | :------ | :--------------------------- |
+| height | `string` | ❌       | 100%    | Height of the YouTube iframe |
+| width  | `string` | ❌       | 315     | Width of the YouTube iframe  |
+
 ## Options
 
 ### customTransformers
@@ -860,6 +869,7 @@ Thanks goes to these people ([emoji key][emojis]):
 
 <!-- markdownlint-enable -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 This project follows the [all-contributors][all-contributors] specification.