Add support for FlexFEC

I have added WebRTC’s FlexFEC module to the Mediasoup,but I don’t know how to enable the flexfec on the libmediasoupclient.
I just know it needs to add “WebRTC-FlexFEC-03/Enabled/WebRTC-FlexFEC-03-Advertised/Enabled”, so what do I need to do next?