Add CodeQL badge

Author: jeromewu

README.md

@@ -8,6 +8,7 @@
 
 [![Node Version](https://img.shields.io/node/v/@ffmpeg/ffmpeg.svg)](https://img.shields.io/node/v/@ffmpeg/ffmpeg.svg)
 [![Actions Status](https://github.com/ffmpegwasm/ffmpeg.wasm/workflows/CI/badge.svg)](https://github.com/ffmpegwasm/ffmpeg.wasm/actions)
+![CodeQL](https://github.com/ffmpegwasm/ffmpeg.wasm/workflows/CodeQL/badge.svg)
 ![npm (tag)](https://img.shields.io/npm/v/@ffmpeg/ffmpeg/latest)
 [![Maintenance](https://img.shields.io/badge/Maintained%3F-yes-green.svg)](https://github.com/ffmpegwasm/ffmpeg.wasm/graphs/commit-activity)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)