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
```
if (this.xfaData) {
      return this.xfaData.bbox;
    }
    const box = this._getInheritableProperty(name,  true);
    if (Array.isArray(box) && box.length === 4) {
      if (box[2] - box[0] !== 0 && box[3] - box[1] !== 0) {
        return box;
      }
      warn(`Empty /${name} entry.`);
    }
    return null;
  }
  get mediaBox() {
    
    return shadow(
      this,
      "mediaBox",
      this._getBoundingBox("MediaBox") || LETTER_SIZE_MEDIABOX
    );
  }
  get cropBox() {
    
    return shadow(
      this,
      "cropBox",
      this._getBoundingBox("CropBox") || this.mediaBox
    );
  }
  get userUnit() {