function _loadJson( fontVariant, jsonUrl ) {

	new external_three_namespaceObject.FileLoader().setResponseType( 'json' ) .load( jsonUrl, ( response ) => {

		fontVariant._buildData( response );
		fontVariant._checkReadiness();

	} );

}
Load a msdf json then build fontVariant data

@param {FontVariant} fontVariant
@param {string} jsonUrl
@private