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
```
expect(data.annotationType).toEqual(AnnotationType.WIDGET
      expect(data.textAlignment).toEqual(null
      expect(data.maxLen).toEqual(null
      expect(data.readOnly).toEqual(false
      expect(data.hidden).toEqual(false
      expect(data.multiLine).toEqual(false
      expect(data.comb).toEqual(false
      expect(data.defaultFieldValue).toEqual("foo"
    }
    it("should not set invalid text alignment, maximum length and flags", async function () {
      textWidgetDict.set("Q", "center"
      textWidgetDict.set("MaxLen", "five"
      textWidgetDict.set("Ff", "readonly"
      const textWidgetRef = Ref.get(43, 0
      const xref = new XRefMock([{ ref: textWidgetRef, data: textWidgetDict }]
      const { data } = await AnnotationFactory.create(
        xref,
        textWidgetRef,
        pdfManagerMock,
        idFactoryMock
      
      expect(data.annotationType).toEqual(AnnotationType.WIDGET
      expect(data.textAlignment).toEqual(null
      expect(data.maxLen).toEqual(null
      expect(data.readOnly).toEqual(false
      expect(data.hidden).toEqual(false
      expect(data.multiLine).toEqual(false
      expect(data.comb).toEqual(false
    }
    it("should set valid text alignment, maximum length and flags", async function () {