misc: add django-upgrade files/notes (#69798)

.pre-commit-config.yaml

@@ -6,6 +6,11 @@ repos:
     hooks:
     - id: pyupgrade
       args: ['--keep-percent-format', '--py37-plus']
+-   repo: https://github.com/adamchainz/django-upgrade
+    rev: 1.10.0
+    hooks:
+    - id: django-upgrade
+      args: ['--target-version', '2.2']
 -   repo: https://github.com/psf/black
     rev: 22.3.0
     hooks:

README

@@ -74,6 +74,10 @@ djhtml is used to automatically indent html files, using those parameters:
 
     djhtml --tabwidth 2
 
+django-upgrade is used to automatically upgrade Django syntax, using those parameters:
+
+    django-upgrade --target-version 2.2
+
 There is .pre-commit-config.yaml to use pre-commit to automatically run these tools
 before commits. (execute `pre-commit install` to install the git hook.)