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 combWidth = (width / this.data.maxLen).toFixed(2);
    const buf = [];
    const positions = font.getCharPositions(text);
    for (const [start, end] of positions) {
      buf.push(`(${escapeString(text.substring(start, end))}) Tj`);
    }
    const renderedComb = buf.join(` ${combWidth} 0 Td `);
    return (
      "/Tx BMC q BT " +
      defaultAppearance +
      ` 1 0 0 1 ${hPadding} ${vPadding} Tm ${renderedComb}` +
      " ET Q EMC"
    );
  }
  _getMultilineAppearance(
    defaultAppearance,
    text,
    font,
    fontSize,
    width,
    height,
    alignment,
    hPadding,
    vPadding