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
```
if (typeof fillAlpha === "number") {
      gsDict.set("ca", fillAlpha);
    }
    const stateDict = new Dict(xref);
    stateDict.set("GS0", gsDict);
    const resources = new Dict(xref);
    resources.set("ExtGState", stateDict);
    resources.set("XObject", formDict);
    const appearanceDict = new Dict(xref);
    appearanceDict.set("Resources", resources);
    const bbox = (this.data.rect = [minX, minY, maxX, maxY]);
    appearanceDict.set("BBox", bbox);
    this.appearance = new StringStream("/GS0 gs /Fm0 Do");
    this.appearance.dict = appearanceDict;
    
    
    this._streams.push(this.appearance, appearanceStream);
  }
}
class WidgetAnnotation extends Annotation {
  constructor(params) {
    super(params);
    const dict = params.dict;
    const data = this.data;
    this.ref = params.ref;
    data.annotationType = AnnotationType.WIDGET;
    if (data.fieldName === undefined) {
      data.fieldName = this._constructFieldName(dict);
    }
    if (data.actions === undefined) {