gui: Fix layout file not being created for the first time on Windows
By ensuring imgui.ini exists. Also enabled u_config_json_open_or_create_file for Windows as this OS has an implementation of u_file_get_path_in_config_dir available now.
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
By ensuring imgui.ini exists. Also enabled u_config_json_open_or_create_file for Windows as this OS has an implementation of u_file_get_path_in_config_dir available now.