Enabling language switcher (#2465)

## Motivation for the change, related issues

The Playground Documentation has support for six different languages
outside English: Japanese, Portuguese, Spanish, Tagalog, and Gujarati.

The pull request enables the Language dropdown in the top-right corner:

<img width="2559" height="1265" alt="Screenshot 2025-08-06 at 11 43 16"
src="https://github.com/user-attachments/assets/591c3a6c-732f-4bb5-a296-51721eefdd1a"
/>

## Testing Instructions (or ideally a Blueprint)

1. Download the branch
2. Run the project locally
3. Find the language dropdown on the top-right
4. Switch the language documentation

Author: fellyph

packages/docs/site/docusaurus.config.js

@@ -167,21 +167,16 @@ const config = {
 						label: 'API Reference',
 						position: 'left',
 					},
-					// {
-					// 	href: 'https://playground.wordpress.net/gutenberg.html',
-					// 	label: 'Gutenberg PR Previewer',
-					// 	position: 'right',
-					// },
 					{
 						href: 'https://github.com/WordPress/wordpress-playground',
 						position: 'right',
 						className: 'header-github-link',
 						'aria-label': 'GitHub repository',
 					},
-					// {
-					// 	type: 'localeDropdown',
-					// 	position: 'right',
-					// },
+					{
+						type: 'localeDropdown',
+						position: 'right',
+					},
 				],
 			},
 			footer: {