Add Websocket option validate_utf8

This allows disabling the UTF-8 validation check
for text and close frames.

test/handlers/ws_dont_validate_utf8_h.erl

@@ -0,0 +1,23 @@
+%% This module disables UTF-8 validation.
+
+-module(ws_dont_validate_utf8_h).
+-behavior(cowboy_websocket).
+
+-export([init/2]).
+-export([websocket_handle/2]).
+-export([websocket_info/2]).
+
+init(Req, State) ->
+	{cowboy_websocket, Req, State, #{
+		validate_utf8 => false
+	}}.
+
+websocket_handle({text, Data}, State) ->
+	{reply, {text, Data}, State};
+websocket_handle({binary, Data}, State) ->
+	{reply, {binary, Data}, State};
+websocket_handle(_, State) ->
+	{ok, State}.
+
+websocket_info(_, State) ->
+	{ok, State}.