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
```
case "BM":
            this.ctx.globalCompositeOperation = value;
            break;
          case "SMask":
            if (this.current.activeSMask) {
              
              
              
              if (
                this.stateStack.length > 0 &&
                this.stateStack[this.stateStack.length - 1].activeSMask ===
                  this.current.activeSMask
              ) {
                this.suspendSMaskGroup();
              } else {
                this.endSMaskGroup();
              }
            }
            this.current.activeSMask = value ? this.tempSMask : null;
            if (this.current.activeSMask) {
              this.beginSMaskGroup();
            }
            this.tempSMask = null;
            break;
          case "TR":
            this.current.transferMaps = value;
        }
      }
    }
    beginSMaskGroup() {