Configuration:
- PDF.js version: 2.0.550

Steps to reproduce the problem:
1. Render document in SVG mode `renderMode="svg"`

What is the expected behavior? (add screenshot)
Rendering annotations same way as they rendered on canvas

What went wrong? (add screenshot)
```
Warning: Unimplemented operator beginAnnotations
Warning: Unimplemented operator endAnnotations
```
constructor(params) {
    super(params);
    
    
    
    this.data.fieldValue = null;
  }
  getFieldObject() {
    return {
      id: this.data.id,
      value: null,
      page: this.data.pageIndex,
      type: "signature",
    };
  }
}
class TextAnnotation extends MarkupAnnotation {