Add default 50ms output_latency web override.

Hopefully a good tradeoff between latency and performance on most
browsers.

servers/audio_server.cpp

@@ -184,6 +184,7 @@ void AudioDriverManager::initialize(int p_driver) {
 	GLOBAL_DEF_RST("audio/enable_audio_input", false);
 	GLOBAL_DEF_RST("audio/mix_rate", DEFAULT_MIX_RATE);
 	GLOBAL_DEF_RST("audio/output_latency", DEFAULT_OUTPUT_LATENCY);
+	GLOBAL_DEF_RST("audio/output_latency.web", 50); // Safer default output_latency for web.
 
 	int failed_driver = -1;