Add maintenante/shfmt.sh for shell script formatting

Thanks @selfhoster1312 <3

maintenance/shfmt.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+shfmt_args=(
+    --indent 4
+    --keep-padding      # keep column alignment paddings
+    --space-redirects   # redirect operators will be followed by a space
+    --binary-next-line  # binary ops like && and | may start a line
+    --case-indent       # switch cases will be indented
+)
+
+shfmt "${shfmt_args[@]}" "$@" \
+    helpers/helpers \
+    helpers/helpers.v2.1.d/* \
+    helpers/helpers.v2.d/* \
+    hooks/*