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 (
      !Number.isInteger(pageNumber) ||
      pageNumber <= 0 ||
      pageNumber > this._numPages
    ) {
      return Promise.reject(new Error("Invalid page request"));
    }
    const pageIndex = pageNumber - 1;
    if (pageIndex in this.pagePromises) {
      return this.pagePromises[pageIndex];
    }
    const promise = this.messageHandler
      .sendWithPromise("GetPage", {
        pageIndex,
      })
      .then(pageInfo => {
        if (this.destroyed) {
          throw new Error("Transport destroyed");
        }
        const page = new PDFPageProxy(
          pageIndex,
          pageInfo,
          this,
          this._params.ownerDocument,
          this._params.pdfBug
        );
        this.pageCache[pageIndex] = page;
        return page;
      });
    this.pagePromises[pageIndex] = promise;