Add missing frame types to websocket_handle specs/docs

Thanks Artem.

doc/src/manual/cowboy_websocket.asciidoc

@@ -31,7 +31,7 @@ Req        :: cowboy_req:req()
 PartialReq :: map()
 State      :: any()
 Opts       :: cowboy_websocket:opts()
-InFrame    :: {text | binary | ping | pong, binary()}
+InFrame    :: ping | pong | {text | binary | ping | pong, binary()}
 OutFrame   :: cow_ws:frame()                    %% see types below
 Info       :: any()
 

src/cowboy_websocket.erl

@@ -47,7 +47,7 @@
 	-> call_result(State) when State::any().
 -optional_callbacks([websocket_init/1]).
 
--callback websocket_handle({text | binary | ping | pong, binary()}, State)
+-callback websocket_handle(ping | pong | {text | binary | ping | pong, binary()}, State)
 	-> call_result(State) when State::any().
 -callback websocket_info(any(), State)
 	-> call_result(State) when State::any().