Expand README
Expand README

Add Features and more info on building, also document samples

awslabs/amazon-kinesis-video-streams-webrtc-sdk-c,awslabs/amazon-kinesis-video-streams-webrtc-sdk-c,awslabs/amazon-kinesis-video-streams-webrtc-sdk-c,awslabs/amazon-kinesis-video-streams-webrtc-sdk-c