Add format script and --check in pre-commit

Author: davegaeddert

scripts/format

@@ -0,0 +1,2 @@
+#!/bin/sh -e
+poetry run black p "$@"

scripts/pre-commit

@@ -1,3 +1,3 @@
 #!/bin/sh -e
-poetry run black p
+./scripts/format --check
 poetry run p --help