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
```
break;
        default:
          throw new Error(`Got unknown object type ${type}`);
      }
      return undefined;
    });
    messageHandler.on("DocProgress", data => {
      if (this.destroyed) {
        return; 
      }
      if (loadingTask.onProgress) {
        loadingTask.onProgress({
          loaded: data.loaded,
          total: data.total,
        });
      }
    });
    messageHandler.on(
      "UnsupportedFeature",
      this._onUnsupportedFeature.bind(this)
    );
    messageHandler.on("FetchBuiltInCMap", data => {
      if (this.destroyed) {
        return Promise.reject(new Error("Worker was destroyed."));
      }
      if (!this.CMapReaderFactory) {
        return Promise.reject(
          new Error(
            "CMapReaderFactory not initialized, see the `useWorkerFetch` parameter."
          )