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.optionalContentConfig = optionalContentConfig;
      this.cachedCanvases = new CachedCanvases(this.canvasFactory);
      if (canvasCtx) {
        
        
        addContextCurrentTransform(canvasCtx);
      }
      this._cachedGetSinglePixelWidth = null;
    }
    beginDrawing({
      transform,
      viewport,
      transparency = false,
      background = null,
    }) {
      
      
      
      
      
      const width = this.ctx.canvas.width;
      const height = this.ctx.canvas.height;
      this.ctx.save();
      this.ctx.fillStyle = background || "rgb(255, 255, 255)";
      this.ctx.fillRect(0, 0, width, height);
      this.ctx.restore();
      if (transparency) {
        const transparentCanvas = this.cachedCanvases.getCanvas(
          "transparent",
          width,