feat: add Django 6.0 support

tox.ini

@@ -7,6 +7,7 @@ envlist =
     py{310,311,312}-django50
     py{310,311,312,313}-django51
     py{310,311,312,313,314}-django52
+    py{312,313,314}-django60
     lint
 
 [gh-actions]
@@ -32,6 +33,7 @@ deps =
     django50: django>=5.0,<5.1
     django51: django>=5.1,<5.2
     django52: django>=5.2,<5.3
+    django60: django>=6.0,<6.1
 
 [testenv:lint]
 basepython = python3.12