message: Add Mirage factory type declaration
diff: +/* tslint:disable max-classes-per-file */
  export { default as faker } from 'faker';
  type ID = number | string;
  @@ -175,7 +176,11 @@ export function trait(options: AnyAttrs & {
  // function association(...traits: string[], overrides?: { [key: string]: any }): unknown;
  export function association(...args: any[]): unknown;
  -export const Factory: any;
  +export class FactoryClass {
  + extend<T>(attrs: AnyAttrs): FactoryClass;
  +}
  +
  +export const Factory: FactoryClass;
  declare global {
  const server: Server; // TODO: only in tests?
  @@ -188,3 +193,4 @@ export class JSONAPISerializer {
  keyForRelationship(relationship: string): string;
  }
  +/* tslint:enable max-classes-per-file */
  