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
```
* Page getTextContent parameters.
 *
 * @typedef {Object} getTextContentParameters
 * @property {boolean} normalizeWhitespace - Replaces all occurrences of
 *   whitespace with standard spaces (0x20). The default value is `false`.
 * @property {boolean} disableCombineTextItems - Do not attempt to combine
 *   same line {@link TextItem}'s. The default value is `false`.
 * @property {boolean} [includeMarkedContent] - When true include marked
 *   content items in the items array of TextContent. The default is `false`.
 */
/**
 * Page text content.
 *
 * @typedef {Object} TextContent
 * @property {Array<TextItem | TextMarkedContent>} items - Array of
 *   {@link TextItem} and {@link TextMarkedContent} objects. TextMarkedContent
 *   items are included when includeMarkedContent is true.
 * @property {Object<string, TextStyle>} styles - {@link TextStyle} objects,
 *   indexed by font name.
 */
/**
 * Page text content part.
 *
 * @typedef {Object} TextItem
 * @property {string} str - Text content.
 * @property {string} dir - Text direction: 'ttb', 'ltr' or 'rtl'.
 * @property {Array<any>} transform - Transformation matrix.
 * @property {number} width - Width in device space.
 * @property {number} height - Height in device space.
 * @property {string} fontName - Font name used by PDF.js for converted font.