Refactor: Rename introduction pages to welcome

Co-authored-by: dan <dan@vapi.ai>

Author: cursoragent

fern/quickstart/introduction.mdx fern/quickstart/welcome.mdxfern/quickstart/introduction.mdx renamed to fern/quickstart/welcome.mdx

@@ -1,7 +1,7 @@
 ---
-title: Introduction
+title: Welcome
 subtitle: Build voice AI agents that can make and receive phone calls
-slug: quickstart/introduction
+slug: quickstart/welcome
 ---
 
 ## What is Vapi?

fern/tools/introduction.mdx fern/tools/welcome.mdxfern/tools/introduction.mdx renamed to fern/tools/welcome.mdx

@@ -1,5 +1,5 @@
 ---
-title: Introduction to Tools
+title: Welcome to Tools
 subtitle: Extend your assistant's capabilities with powerful function calling tools.
 slug: tools
 ---
@@ -104,4 +104,4 @@ Common use cases include:
   >
     Get help with tool integrations from our community
   </Card>
-</CardGroup> 
+</CardGroup>