message: fix type of default class Base
  defaultClasses(src): Base: fix type of "__v" & "__t"
  defaultClasses(src): FindOrCreate: replace type with "AnyParamConstructor"
  fixes typegoose/typegoose#208
diff: import type { Types } from 'mongoose';
  import { modelOptions } from './modelOptions';
  -import type { DocumentType, RefType } from './types';
  +import type { AnyParamConstructor, DocumentType, RefType } from './types';
  @modelOptions({ schemaOptions: { timestamps: true } })
  /**
  @@ -18,9 +18,9 @@ export abstract class TimeStamps {
  export abstract class Base<T_ID extends RefType = Types.ObjectId> {
  public _id: T_ID;
  // tslint:disable-next-line:variable-name
  - public __v: number;
  + public __v?: number;
  // tslint:disable-next-line:variable-name
  - public __t: undefined | string | number;
  + public __t?: string | number;
  }
  export interface FindOrCreateResult<T> {
  @@ -33,7 +33,7 @@ export interface FindOrCreateResult<T> {
  */
  export abstract class FindOrCreate {
  public static findOrCreate: <T extends FindOrCreate>(
  - this: new (...a: any[]) => T,
  + this: AnyParamConstructor<T>,
  condition: any
  ) => Promise<FindOrCreateResult<T>>;
  }
  