add link to vercel marketplace

Author: isshaddad

docs/vercel-integration.mdx

@@ -52,7 +52,7 @@ You can connect Vercel from two entry points:
 <Steps>
 
 <Step title="Install the integration">
-  Find Trigger.dev on the Vercel Marketplace and install it. This will redirect you to Trigger.dev to complete setup.
+  Install the [Trigger.dev integration from the Vercel Marketplace](https://vercel.com/marketplace/trigger). This will redirect you to Trigger.dev to complete setup.
 </Step>
 
 <Step title="Select your Trigger.dev organization and project">