feat: support --fake for aerich upgrade (#398)

* feat: support `--fake` for aerich upgrade

* Add `--fake` to downgrade

* tests: check --fake result for aerich upgrade and downgrade

* Update readme

* Fix unittest failed because of `db_field_types` changed

* refactor: improve type hints and document

tests/old_models.py

@@ -52,6 +52,7 @@ class Category(Model):
     user: fields.ForeignKeyRelation[User] = fields.ForeignKeyField(
         "models.User", description="User"
     )
+    title = fields.CharField(max_length=20, unique=True)
     created_at = fields.DatetimeField(auto_now_add=True)