Add Django 4.2 to test matrix (#374)

Author: asherf

pyproject.toml

@@ -22,7 +22,7 @@ line-length = 120
 legacy_tox_ini = """
 [tox]
 min_version = 4.4
-envlist = {py37,py38,py39,py310,py311}-django{320}-{end2end,unittests},{py38,py39,py310,py311}-django{400,410}-{end2end,unittests},py39-lint
+envlist = {py37,py38,py39,py310,py311}-django{320}-{end2end,unittests},{py38,py39,py310,py311}-django{400,410,420}-{end2end,unittests},py39-lint
 
 [gh-actions]
 python =
@@ -37,6 +37,7 @@ deps =
     django320: Django>=3.2,<3.3
     django400: Django>=4.0,<4.1
     django410: Django>=4.1,<4.2
+    django420: Django>=4.2,<4.3
     coverage
     -rrequirements.txt
 skip_missing_interpreters=true