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 stream = this.stream;
    stream.reset();
    if (!find(stream, PDF_HEADER_SIGNATURE)) {
      
      
      return;
    }
    stream.moveStart();
    
    const MAX_PDF_VERSION_LENGTH = 12;
    let version = "",
      ch;
    while ((ch = stream.getByte()) >  0x20) {
      if (version.length >= MAX_PDF_VERSION_LENGTH) {
        break;
      }
      version += String.fromCharCode(ch);
    }
    if (!this._version) {
      
      this._version = version.substring(5);
    }
  }
  parseStartXRef() {