message: docs(prop): fix invalid default function example
diff: @@ -79,8 +79,13 @@ Example:
  ```ts
  class Defaulted {
  + @prop({ required: true })
  + firstName!: string
  + @prop({ required: true })
  + lastName!: string
  +
  @prop({
  - default: (this: DocumentType<Defaulted>) => {
  + default: function (this: DocumentType<Defaulted>) {
  return `${this.firstName} ${this.lastName}`
  }
  })
  