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
```
this._lastProgress = {
          loaded: evt.loaded,
          total: evt.total,
        };
      };
      sink.onPull = () => {
        this._fullReader
          .read()
          .then(function ({ value, done }) {
            if (done) {
              sink.close();
              return;
            }
            assert(
              isArrayBuffer(value),
              "GetReader - expected an ArrayBuffer."
            );
            
            
            sink.enqueue(new Uint8Array(value), 1, [value]);
          })
          .catch(reason => {
            sink.error(reason);
          });
      };
      sink.onCancel = reason => {
        this._fullReader.cancel(reason);
        sink.ready.catch(readyReason => {
          if (this.destroyed) {
            return;