message: added new badge: jsdelivr downloads
diff: -[![npm version](https://img.shields.io/npm/v/pptxgenjs.svg)](https://www.npmjs.com/package/pptxgenjs) [![MIT Licence](https://img.shields.io/github/license/gitbrent/pptxgenjs.svg)](https://opensource.org/licenses/mit-license.php) [![npm downloads](https://img.shields.io/npm/dm/pptxgenjs.svg)](https://www.npmjs.com/package/pptxgenjs) [![Package Quality](http://npm.packagequality.com/shield/pptxgenjs.png?style=flat-square)](https://github.com/gitbrent/pptxgenjs)
  +[![npm version](https://img.shields.io/npm/v/pptxgenjs.svg)](https://www.npmjs.com/package/pptxgenjs) [![MIT Licence](https://img.shields.io/github/license/gitbrent/pptxgenjs.svg)](https://opensource.org/licenses/mit-license.php) [![npm downloads](https://img.shields.io/npm/dm/pptxgenjs.svg)](https://www.npmjs.com/package/pptxgenjs) [![jsdelivr downloads](https://data.jsdelivr.com/v1/package/gh/gitbrent/pptxgenjs/badge)](https://www.jsdelivr.com/package/gh/gitbrent/pptxgenjs) [![Package Quality](http://npm.packagequality.com/shield/pptxgenjs.png?style=flat-square)](https://github.com/gitbrent/pptxgenjs)
  # PptxGenJS
  