message: extend method missing options param
  Typescript definition is missing options as a third parameter. Therefore it is not possible to bind target parameter for custom validations such as custom confirmed validator. This fix is to solve this issue in typescript.
diff: @@ -138,7 +138,7 @@ export class Validator {
  attach(options: FieldOptions): Field;
  reset(matcher?: FieldMatchOptions): Promise<void>;
  detach(name: string, scope?: string): void;
  - extend(name: string, validator: Object|Function): void;
  + extend(name: string, validator: Object|Function, options?:ExtendOptions): void;
  flag(name: string, flags: Object): void;
  pause(): Validator;
  remove(name: string): void;
  @@ -151,13 +151,17 @@ export class Validator {
  validateAll(values?: Object, scope?: string, silent?: boolean): Promise<any>;
  validateScopes(silent?: boolean): Promise<any>;
  static create(validations: Object, options: any): Validator;
  - static extend(name: string, validator: Object|Function): void;
  + static extend(name: string, validator: Object|Function, options?:ExtendOptions): void;
  static remove(name: string): void;
  static setStrictMode(strictMode?: boolean): void;
  static localize(rootDictionary: Object): void;
  static localize(language: string, dictionary?: Object): void;
  }
  +export class ExtendOptions {
  + hasTarget?: boolean
  +};
  +
  export const version: string;
  export const install: Vue.PluginFunction<never>
  