Add PDM post_install hook

Ensures that dependencies in pyproject.toml stay sorted.

pyproject.toml

@@ -76,6 +76,10 @@ doc.shell = "cd docs && mkdocs serve -a localhost:8030"
 lint.help = "Run linters over all files"
 lint.cmd = "pre-commit run --all-files"
 
+# PDM hook to automatically sort dependencies when they change.
+# "true" is there since GitHub Actions will fail if this returns a non-zero exit code.
+post_install.shell = "pre-commit run keep-sorted --files pyproject.toml > /dev/null 2> /dev/null; true"
+
 #
 # Aeromancy-specific scripts.
 #