Added typings doesn't compile in TS in Angular@5

[ma2ciek]

Being concrete this line:

on( event: string, callback: ( ...args: any ) => any ): void;

should be changed to the following:

on( event: string, callback: ( ...args: any[] ) => any ): void;

to make the old TS compiler happy.

Sadly, the package builder which should compile packages working with Angular@5 can't find such mistakes.