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 (j >= signatureLength) {
        
        stream.pos += pos - signatureEnd;
        return true;
      }
      pos--;
    }
  } else {
    
    let pos = 0;
    while (pos <= scanLength) {
      let j = 0;
      while (j < signatureLength && scanBytes[pos + j] === signature[j]) {
        j++;
      }
      if (j >= signatureLength) {
        
        stream.pos += pos;
        return true;
      }
      pos++;
    }
  }
  return false;
}
/**
 * The `PDFDocument` class holds all the (worker-thread) data of the PDF file.
 */
class PDFDocument {