add clean django-stubs folder, add some tests

django-stubs/db/models/fields/__init__.pyi

@@ -0,0 +1,26 @@
+from typing import Any
+
+from django.db.models.query_utils import RegisterLookupMixin
+
+
+class Field(RegisterLookupMixin):
+    def __init__(self,
+                 primary_key: bool = False,
+                 **kwargs): ...
+    def __get__(self, instance, owner) -> Any: ...
+
+
+class IntegerField(Field):
+    def __get__(self, instance, owner) -> int: ...
+
+
+class AutoField(Field):
+    def __get__(self, instance, owner) -> int: ...
+
+
+class CharField(Field):
+    def __init__(self,
+                 max_length: int,
+                 **kwargs): ...
+    def __get__(self, instance, owner) -> str: ...
+