Mongoose 7.2

• Added mg_mqtt_next_unsub()
• Added chunked HTTP client support and MG_EV_HTTP_CHUNK event
• Restored mg_mqtt_{ping,pong,disconnect} functions
• Fixed Cygwin and QNX builds
• Added struct mg_mgr::userdata pointer
• Added struct mg_http_message::head which contains HTTP line and all headers
• Add ability to use in-memory CA PEM for mbedtls
• Improved unicode handling on Win32
• Improved ESP32 example to use SPIFFS and static serving
• Improved TLS SNI