Add upgrade-python recipe

Author: seddonym

justfile

@@ -151,6 +151,12 @@ show-benchmark-results:
 benchmark-ci:
     @uv run --group=benchmark-ci pytest --codspeed
 
+# Upgrade code to latest supported version.
+# E.g. find
+[group('maintenance')]
+upgrade-python MIN_VERSION:
+    find {docs,src,tests} -name "*.py" -not -path "tests/assets/*" -exec uv run pyupgrade --py{{MIN_VERSION}}-plus {} +
+
 # Run all linters, build docs and tests. Worth running before pushing to Github.
 [group('prepush')]
 full-check: