🚀 Enhancement: Add Mailgun email notification function template-Python

### 🔖 Enhancement description

The template should provide a ready-to-use function utilizing the Mailgun Python API to send out emails automatically when specific events occur in an Appwrite project (e.g., document creation, object creation etc.). The function should be easily configurable with Mailgun credentials and support customizable email content.

### 🎤 Pitch

When a user submits a form or completes an action in an application, the Appwrite function would trigger and send a notification email using Mailgun upon **document creation** event. This is ideal for applications needing transactional email notifications or confirmations, saving setup time.

### 👀 Have you spent some time to check if this issue has been raised before?

- [x] I checked and didn't find similar issue

### 🏢 Have you read the Code of Conduct?

- [x] I have read the [Code of Conduct](https://github.com/appwrite/.github/blob/main/CODE_OF_CONDUCT.md)