Update plugin tracking refs to unique identifiers

Changed generic ?ref=plugin to plugin-specific ?ref=plugin_{name} for better tracking and analytics.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: riderx

README.md

@@ -2,8 +2,8 @@
  <a href="https://capgo.app/"><img src='https://raw.githubusercontent.com/Cap-go/capgo/main/assets/capgo_banner.png' alt='Capgo - Instant updates for capacitor'/></a>
 
 <div align="center">
-  <h2><a href="https://capgo.app/?ref=plugin"> ➡️ Get Instant updates for your App with Capgo</a></h2>
-  <h2><a href="https://capgo.app/consulting/?ref=plugin"> Missing a feature? We’ll build the plugin for you 💪</a></h2>
+  <h2><a href="https://capgo.app/?ref=plugin_pay"> ➡️ Get Instant updates for your App with Capgo</a></h2>
+  <h2><a href="https://capgo.app/consulting/?ref=plugin_pay"> Missing a feature? We’ll build the plugin for you 💪</a></h2>
 </div>
 
 Capacitor plugin to trigger native payments with Apple Pay and Google Pay using a unified JavaScript API.