feat: add some precommit (#274)

- ensure correct formatting with shfmt
- ensure correct syntax with shellcheck

Co-authored-by: damien cavagnini <damien.cavagnini@corp.ovh.com>

hooks/shfmt.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+for script in "$@"; do
+    shfmt -l -i 4 -w "$script"
+done
+
+exit 0