🚀 BREAKING: Simplify API to use Payload collections directly

- Remove complex sendEmail/scheduleEmail methods and SendEmailOptions types
- Add simple renderTemplate() helper for template rendering
- Users now create emails using payload.create() with full type safety
- Leverage Payload's existing collection system instead of duplicating functionality
- Provide comprehensive migration guide and usage examples

BREAKING CHANGES:
- sendEmail() and scheduleEmail() methods removed
- SendEmailOptions type removed
- Use payload.create() with email collection instead
- Use renderTemplate() helper for template rendering

Benefits:
✅ Full TypeScript support with generated Payload types
✅ Use any custom fields in your email collection
✅ Leverage Payload's validation, hooks, and access control
✅ Simpler, more consistent API
✅ Less code to maintain

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

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@xtr-dev/payload-mailing",
-  "version": "0.0.12",
+  "version": "0.1.0",
   "description": "Template-based email system with scheduling and job processing for PayloadCMS",
   "type": "module",
   "main": "dist/index.js",