docs: add supported syntax highlighting languages for custom code samples

Co-Authored-By: Chris McDonnell <[email protected]>

Author: devin-ai-integration[bot]

fern/products/api-def/openapi-pages/extensions/examples.mdx

@@ -68,3 +68,20 @@ paths:
 
                 client.users.get("user-1234")
 ```
+
+#### Supported languages
+
+Fern supports syntax highlighting for the following languages in custom code samples:
+
+- `curl`
+- `python`
+- `javascript` (aliases: `js`, `node`)
+- `typescript` (aliases: `ts`)
+- `go`
+- `ruby`
+- `csharp`
+- `php`
+- `swift`
+- `rust`
+
+If you specify a language that is not in this list, Fern will still display the code sample but without syntax highlighting.