Allow hacking to be used as a pre-commit hook

This allows hacking to be used the same way flake8 is used as
a pre-commit hook. This allows repository owners to control bumping
using `pre-commit auto-update` when they feel appropriate.

Change-Id: Id00b79ff3006c390f925dcc5031ac503374cf9bd
Needed-By: https://review.opendev.org/c/openstack/tripleo-heat-templates/+/783828

.pre-commit-hooks.yaml

@@ -0,0 +1,12 @@
+- id: hacking
+  name: hacking
+  description: 'Runs hacking, the OpenStack blend of flake8'
+  entry: flake8
+  language: python
+  types: [python]
+  require_serial: true
+  additional_dependencies:
+    # This enables the pep257 extra from hacking by default. If you want
+    # to avoid it, just override additional_dependencies in your hook config
+    # by listing only `- .`. We assume that most users want this feature.
+    - .[pep257]