Document ping and pong handler argument
Document ping and pong handler argument

Closes #76

huuzkee-foundation/websocket,your-org/websocket,skyportsystems/websocket,vonwenm/websocket-1,Janipro/websocket,beni55/websocket,helight/helight_code,helight/helight_code,gorilla/websocket,helight/helight_code,helight/helight_code,zombiezen/websocket,helight/helight_code,helight/helight_code,y3llowcake/websocket,helight/helight_code,helight/helight_code,helight/helight_code