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
```
return this.messageHandler.sendWithPromise("GetPageLabels", null);
  }
  getPageLayout() {
    return this.messageHandler.sendWithPromise("GetPageLayout", null);
  }
  getPageMode() {
    return this.messageHandler.sendWithPromise("GetPageMode", null);
  }
  getViewerPreferences() {
    return this.messageHandler.sendWithPromise("GetViewerPreferences", null);
  }
  getOpenAction() {
    return this.messageHandler.sendWithPromise("GetOpenAction", null);
  }
  getAttachments() {
    return this.messageHandler.sendWithPromise("GetAttachments", null);
  }
  getJavaScript() {
    return this.messageHandler.sendWithPromise("GetJavaScript", null);
  }
  getDocJSActions() {
    return this.messageHandler.sendWithPromise("GetDocJSActions", null);
  }
  getPageJSActions(pageIndex) {
    return this.messageHandler.sendWithPromise("GetPageJSActions", {
      pageIndex,
    });
  }
  getStructTree(pageIndex) {