Update Swift SDK availability in documentation

- Change alt text from 'Request Swift' to 'Swift' in introduction.mdx
- Add swift and php to default-language options in what-is-docs-yml.mdx

The Swift SDK is now available and should be consistently represented
throughout the documentation alongside other supported languages.

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

Author: devin-ai-integration[bot]

fern/products/docs/pages/customization/what-is-docs-yml.mdx

@@ -103,7 +103,7 @@ navbar-links:
 <ParamField path="default-language" type="string" required={false} toc={true}>
   Sets the default language displayed by code snippets in the API Reference.
 
-  Options include: `typescript`, `python`, `java`, `go`, `ruby`, `csharp`, `curl`
+  Options include: `typescript`, `python`, `java`, `go`, `ruby`, `csharp`, `php`, `swift`, `curl`
 </ParamField>
 
 <ParamField path="metadata" type="object" required={false} toc={true}>

fern/products/sdks/introduction.mdx

@@ -192,8 +192,8 @@ description: Generate idiomatic SDKs in multiple programming languages
     </a>
     <a class="fern-card interactive not-prose relative block p-6 text-base" href="/sdks/generators/swift/quickstart">
       <div class="flex items-start flex-col space-y-3">
-        <img class="mx-auto dark:hidden" alt="Request Swift" src="./images/swift-card.png" />
-        <img class="mx-auto hidden dark:block" alt="Request Swift" src="./images/swift-card-dark.png" />
+        <img class="mx-auto dark:hidden" alt="Swift" src="./images/swift-card.png" />
+        <img class="mx-auto hidden dark:block" alt="Swift" src="./images/swift-card-dark.png" />
         <div class="w-full space-y-1 overflow-hidden flex justify-between items-center">
           <div class="text-(color:--grayscale-a12) text-body text-base font-semibold card-title">
             Swift