docs: add workflow documentation images and examples (#463)

Co-authored-by: Jimmy Chan <[email protected]>

Author: jimmyechan

fern/static/images/.DS_Store

@@ -9,6 +9,10 @@ description: Build a simple agent that greets users and gathers basic informatio
 
 Build a simple voice agent using Vapi's visual workflow builder that greets users, collects their information, and demonstrates core workflow concepts like variable extraction, conditional routing, and global nodes.
 
+<Frame>
+  <img src="../static/images/workflows/workflows-quickstart-flow.png" alt="Vapi Workflows" />
+</Frame>
+
 **Agent Capabilities:**
 * Greet users and ask about their voice agent needs
 * Extract and store user information (name and city)