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
```
const type = this.data.combo ? "combobox" : "listbox";
    const value =
      this.data.fieldValue.length > 0 ? this.data.fieldValue[0] : null;
    return {
      id: this.data.id,
      value,
      defaultValue: this.data.defaultFieldValue,
      editable: !this.data.readOnly,
      name: this.data.fieldName,
      rect: this.data.rect,
      numItems: this.data.fieldValue.length,
      multipleSelection: this.data.multiSelect,
      hidden: this.data.hidden,
      actions: this.data.actions,
      items: this.data.options,
      page: this.data.pageIndex,
      type,
    };
  }
}
class SignatureWidgetAnnotation extends WidgetAnnotation {