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
```
thisChunkHeight = FULL_CHUNK_HEIGHT;
      elemsInThisChunk = width * thisChunkHeight;
      for (i = 0; i < totalChunks; i++) {
        if (i >= fullChunks) {
          thisChunkHeight = partialChunkHeight;
          elemsInThisChunk = width * thisChunkHeight;
        }
        destPos = 0;
        for (j = elemsInThisChunk; j--; ) {
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = 255;
        }
        if (hasTransferMaps) {
          for (let k = 0; k < destPos; k += 4) {
            if (transferMapRed) {
              dest[k + 0] = transferMapRed[dest[k + 0]];
            }
            if (transferMapGreen) {
              dest[k + 1] = transferMapGreen[dest[k + 1]];
            }
            if (transferMapBlue) {
              dest[k + 2] = transferMapBlue[dest[k + 2]];
            }
          }
        }
        ctx.putImageData(chunkImgData, 0, i * FULL_CHUNK_HEIGHT);
      }
    } else {