✨ FEATURE: Add PayloadCMS task for queuing template emails

- Add sendTemplateEmailTask with comprehensive input schema
- Support template rendering, email parsing, and scheduling
- Include TypeScript interface SendTemplateEmailInput for type safety
- Add task to exports for easy import and usage
- Support custom email collection fields via extensible input
- Add comprehensive documentation with usage examples

Users can now:
✅ Import and add task to their Payload jobs configuration
✅ Queue emails programmatically via payload.jobs.queue()
✅ Use admin panel form interface for manual email queuing
✅ Get full TypeScript support with proper input types
✅ Extend with custom fields from their email collection

Example usage:
```typescript
import { sendTemplateEmailTask } from '@xtr-dev/payload-mailing'

// Add to Payload config
export default buildConfig({
  jobs: { tasks: [sendTemplateEmailTask] }
})

// Queue from code
await payload.jobs.queue({
  task: 'send-template-email',
  input: {
    templateSlug: 'welcome',
    to: ['user@example.com'],
    variables: { name: 'John' }
  }
})
```

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

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

README.md

@@ -598,6 +598,81 @@ await processEmails(payload)
 await retryFailedEmails(payload)
 ```
 
+## PayloadCMS Task Integration
+
+The plugin provides a ready-to-use PayloadCMS task for queuing template emails:
+
+### 1. Add the task to your Payload config
+
+```typescript
+import { buildConfig } from 'payload/config'
+import { sendTemplateEmailTask } from '@xtr-dev/payload-mailing'
+
+export default buildConfig({
+  // ... your config
+  jobs: {
+    tasks: [
+      sendTemplateEmailTask,
+      // ... your other tasks
+    ]
+  }
+})
+```
+
+### 2. Queue emails from your code
+
+```typescript
+import type { SendTemplateEmailInput } from '@xtr-dev/payload-mailing'
+
+// Queue a template email
+const result = await payload.jobs.queue({
+  task: 'send-template-email',
+  input: {
+    templateSlug: 'welcome-email',
+    to: ['user@example.com'],
+    cc: ['manager@example.com'],
+    variables: {
+      firstName: 'John',
+      activationUrl: 'https://example.com/activate/123'
+    },
+    priority: 1,
+    // Add any custom fields from your email collection
+    customField: 'value'
+  } as SendTemplateEmailInput
+})
+
+// Queue a scheduled email
+await payload.jobs.queue({
+  task: 'send-template-email',
+  input: {
+    templateSlug: 'reminder-email',
+    to: ['user@example.com'],
+    variables: { eventName: 'Product Launch' },
+    scheduledAt: new Date('2024-01-15T10:00:00Z').toISOString(),
+    priority: 3
+  }
+})
+```
+
+### 3. Use in admin panel workflows
+
+The task can also be triggered from the Payload admin panel with a user-friendly form interface that includes:
+- Template slug selection
+- Email recipients (to, cc, bcc)
+- Template variables as JSON
+- Optional scheduling
+- Priority setting
+- Any custom fields you've added to your email collection
+
+### Task Benefits
+
+- ✅ **Easy Integration**: Just add to your tasks array
+- ✅ **Type Safety**: Full TypeScript support with `SendTemplateEmailInput`
+- ✅ **Admin UI**: Ready-to-use form interface
+- ✅ **Flexible**: Supports all your custom email collection fields
+- ✅ **Error Handling**: Comprehensive error reporting
+- ✅ **Queue Management**: Leverage Payload's job queue system
+
 ## Job Processing
 
 The plugin automatically adds a unified email processing job to PayloadCMS: