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
```
constructor() {
    this._objs = Object.create(null);
  }
  /**
   * Ensures there is an object defined for `objId`.
   * @private
   */
  _ensureObj(objId) {
    if (this._objs[objId]) {
      return this._objs[objId];
    }
    return (this._objs[objId] = {
      capability: createPromiseCapability(),
      data: null,
      resolved: false,
    });
  }
  /**
   * If called *without* callback, this returns the data of `objId` but the
   * object needs to be resolved. If it isn't, this method throws.
   *
   * If called *with* a callback, the callback is called with the data of the
   * object once the object is resolved. That means, if you call this method
   * and the object is already resolved, the callback gets called right away.
   */
  get(objId, callback = null) {