[Bug] base64 image on markdown

### Bug Description

if i try to set on a markdown image a base64 image, they will not be desplayed on the editor

### How to Reproduce

you can test it with code bellow

```
var markdowntest2 = "";

late EditorStateCustom editorState = EditorStateCustom(
document: markdownToDocument(markdowntest2),
);
```

### Expected Behavior

would be helpfully to display also base64 images

### Operating System

macOS App

### AppFlowy Editor Version(s)

5.1.0

### Screenshots

_No response_

### Additional Context

_No response_