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 groupCtx = this.current.resumeSMaskCtx;
      const currentCtx = this.ctx;
      this.ctx = groupCtx;
      this.groupStack.push(currentCtx);
      this.groupLevel++;
    }
    endSMaskGroup() {