[Help wanted] Translate 'file-backup' function from Python to Dart 🏹

[Glide7]

Translate 'file-backup' function from Python to Dart 🏹

We use Appwrite Cloud Functions demos as a good way to show how Cloud Functions can be used with Appwrite, and also as a good starting point for developers wanting to write their new functions.
Help us translate the cloud function 'file-backup' from Python to Dart ☁

Requirements 🔎

• For testing your code, you need a running Appwrite instance with cloud functions enabled. You’ll need to setup Appwrite from source using the 0.7.x branch and Docker. 🐳
  Clone the appwrite/appwrite 0.7.x branch. More instruction about how to start your Appwrite server from source are available here. 💻

• 
If this is your first PR for Appwrite, it is best to read some of our contributions guidelines.
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• 
For each target language we provide with a template for starting a new function. For Dart you can use this template as your starting point. 🥰

[gat786]

Hey I would like to contribute to this :-)