FFmpeg  Attributes Not Working
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**Describe The Bug:**
Since v2.0.0, `packetSize` seems to be removed from the `ffmpeg` command.  Not sure if intentional or not.

v2.0.0: https://github.com/homebridge-plugins/homebridge-camera-ffmpeg/blob/ee2429e696988a931ec2738e1ed151a5f08d7d62/src/streamingDelegate.ts#L322-L323
No `this.ffmpegOpt.packetSize`

v1.3.0: https://github.com/homebridge-plugins/homebridge-camera-ffmpeg/blob/2d07a3899059ae2c4326bc7d985de5af5d3228ae/ffmpeg.js#L391

However `README` still reference `packetSize`
https://github.com/homebridge-plugins/homebridge-camera-ffmpeg/blame/master/README.md#L106

**Expected behavior:**
Either `packetSize` is removed from `README` or is re-added to `streamingDelegate.ts`
