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
```
it("should parse IRT/RT for a reply type", async function () {
      const annotationRef = Ref.get(819, 0
      const annotationDict = new Dict(
      annotationDict.set("Type", Name.get("Annot")
      annotationDict.set("Subtype", Name.get("Text")
      annotationDict.set("T", "ParentTitle"
      annotationDict.set("Contents", "ParentText"
      annotationDict.set("CreationDate", "D:20180423"
      annotationDict.set("M", "D:20190423"
      annotationDict.set("C", [0, 0, 1]
      const popupRef = Ref.get(820, 0
      const popupDict = new Dict(
      popupDict.set("Type", Name.get("Annot")
      popupDict.set("Subtype", Name.get("Popup")
      popupDict.set("Parent", annotationRef
      annotationDict.set("Popup", popupRef
      const replyRef = Ref.get(821, 0
      const replyDict = new Dict(
      replyDict.set("Type", Name.get("Annot")
      replyDict.set("Subtype", Name.get("Text")
      replyDict.set("IRT", annotationRef
      replyDict.set("RT", Name.get("R")
      replyDict.set("T", "ReplyTitle"
      replyDict.set("Contents", "ReplyText"
      replyDict.set("CreationDate", "D:20180523"
      replyDict.set("M", "D:20190523"
      replyDict.set("C", [0.4]
      const xref = new XRefMock([
        { ref: annotationRef, data: annotationDict },
        { ref: popupRef, data: popupDict },