Include instruction how to extend vfiles
Include instruction how to extend vfiles

dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,mcliment/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,magny/DefinitelyTyped,borisyankov/DefinitelyTyped,georgemarshall/DefinitelyTyped,borisyankov/DefinitelyTyped,magny/DefinitelyTyped,georgemarshall/DefinitelyTyped,markogresak/DefinitelyTyped