🚀 Feature: Adding Random Mesh Gradient as a Background Image

### 🔖 Feature description

There are two options provided as of now for the background of the canvas!
- BG DARK 1 (Appwrite theme Background)
- Custom Image

It would be really amazing if there is something like Mesh Gradient Which looks stunning as a background of the code.
It would be colorful and can have a regenerate button to regenerate to other colors or patterns.

### 🎤 Pitch

It's possible to add Mesh Gradient Background which looks stunning.

### If it's possible then Why do we need this feature?
- In order to do the same we need a mesh gradient generator
- we generate the background and download it to our system
- then we upload to Snapwrite
- and finally, we get our work done

There should be a new option in the `BackgroundImage` dropdown like Mesh Gradient and on the spot generate a brand new Mesh Gradient Background.

### 👀 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)

まず、Snapwriteアプリケーション内のBackgroundImageドロップダウンとcanvasの背景処理を特定します。Mesh Gradientの生成および再生成の動作を定義し、新しいMesh Gradientオプションによって、新しく生成された背景を持つダウンロード可能なコード画像が生成されることを確認します。

索引モデルが issue の本文から書いたものです。