IMP(shfmt): add shell formatter

lib/shellfmt/launch_shellfmt.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+# run-shellcheck
+
+if [ ! -f tmp/shfmt ]; then
+    wget -O tmp/shfmt https://github.com/mvdan/sh/releases/download/v3.2.0/shfmt_v3.2.0_linux_amd64
+fi
+
+chmod +x tmp/shfmt
+
+files=""
+retval=0
+
+if [ "$#" -eq 0 ]; then
+    files=$(find . -name "*.sh" | sort -V)
+else
+    files="$*"
+fi
+
+for f in $files; do
+    ./tmp/shfmt -l -i 4 -w "$f"
+done
+
+exit "$retval"