Add prepare-commit-msg hook

Added new hook for templating prepare-commit-msg hook. Added 2
templates to use keepgin `prepare_commit_msg_append.j2`as default.

The idea is that developers could create their own templates accordingly
to teams commit conventions and override them in the hook arguments when
configuring it.

.pre-commit-hooks.yaml

@@ -174,6 +174,12 @@
     language: python
     pass_filenames: false
     always_run: true
+-   id: prepare-commit-msg
+    name: prepare commit message
+    description: Formatter Helper for your commit message
+    entry: prepare-commit-msg
+    language: python
+    stages: [prepare-commit-msg]
 -   id: requirements-txt-fixer
     name: fix requirements.txt
     description: sorts entries in requirements.txt.