Update README.md with comprehensive documentation and cleanup test files

- Added Discord & Slack notifications section with configuration guide
- Documented multiple phone numbers per workflow feature
- Updated version to 2.1.0 with full changelog
- Enhanced configuration sections for new features
- Added database structure documentation for twp_workflow_phones table
- Removed obsolete test files (test-sdk.php, test-capabilities.php, test-ajax-response.php)
- Updated plugin header with new version and repository URL

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

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

twilio-wp-plugin.php

@@ -1,10 +1,10 @@
 <?php
 /**
  * Plugin Name: Twilio WP Plugin
- * Plugin URI: https://example.com/twilio-wp-plugin
+ * Plugin URI: https://repo.anhonesthost.net/wp-plugins/twilio-wp-plugin
  * Description: WordPress plugin for Twilio integration with phone scheduling, call forwarding, queue management, and Eleven Labs TTS
- * Version: 1.0.0
- * Author: Your Name
+ * Version: 2.1.0
+ * Author: Josh Knapp
  * License: GPL v2 or later
  * Text Domain: twilio-wp-plugin
  */