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
```
const defaultPromise = defaultLoadingTask.promise.then(function (pdfDoc) {
        return pdfDoc.getPage(1).then(function (pdfPage) {
          return pdfPage.getAnnotations();
        });
      });
      const docBaseUrlLoadingTask = getDocument(
        buildGetDocumentParams(filename, {
          docBaseUrl: "http://www.example.com/test/pdfs/qwerty.pdf",
        })
      );
      const docBaseUrlPromise = docBaseUrlLoadingTask.promise.then(function (
        pdfDoc
      ) {
        return pdfDoc.getPage(1).then(function (pdfPage) {
          return pdfPage.getAnnotations();
        });
      });
      const invalidDocBaseUrlLoadingTask = getDocument(
        buildGetDocumentParams(filename, {
          docBaseUrl: "qwerty.pdf",
        })
      );
      const invalidDocBaseUrlPromise =
        invalidDocBaseUrlLoadingTask.promise.then(function (pdfDoc) {
          return pdfDoc.getPage(1).then(function (pdfPage) {
            return pdfPage.getAnnotations();
          });
        });
      const [
        defaultAnnotations,