title: Text choices attribute not recognised
body: <p>I'm trying to create a model with <code>django-multiselectfield</code>, but when I run</p>
  <p><code>python manage.py runserver</code></p>
  <p>I get an error saying :</p>
  <p><code>AttributeError: module 'django.db.models' has no attribute 'TextChoices'</code>.</p>
  <p>I successfully installed <code>django-multiselectfield-0.1.10</code> and I can't figure out why I get this error. Thanks for any help!</p>
  <pre><code>from django.db import models
  from multiselectfield import MultiSelectField
  
  
  class MovieGenre(models.TextChoices):
          Action = 'Action'
          Horror = 'Horror'
          Comedy = 'Comedy'
  
   genre = MultiSelectField(
          choices=MovieGenre.choices,
          max_choices=3,
          min_choices=1
      )
      def __str__(self):
          return self.question_text
  </code></pre>