feat: add support for soft deleted entities

[ld-codes]

Handles https://github.com/SoftwareBrothers/adminjs-typeorm/issues/54

Sometimes you might want to find entities that soft deleted. You can extend the existing entity with withDeleted property:

@Entity()
export class Person extends BaseEntity {
  @DeleteDateColumn()
  deletedAt: Date|null;
}
// admin person model
@Entity('person')
export class AdminPagePerson extends Person {
  static withDeleted = true

  // or method
  static withDeleted() {
    return true
  }
}

If model's withDeleted is true or a function that returns true, then Resource class will add withDeleted: true param to the all typeorm repository methods.