FEAT: automate shellcheck test with docker

IMP: search for all .sh files to shellcheck
If no file is passed as argument, shellchek will be run on all
.sh files

Fix dockerfile location and expand full shellcheck options

shellcheck/launch_shellcheck.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+
+files=""
+
+if [ $# -eq 0 ]; then
+    files=$(find . -name "*.sh")
+else
+    files="$*"
+fi
+
+for f in $files; do
+    printf "\e[1;36mRunning shellcheck on: %s  \e[0m\n" "$f"
+    /usr/bin/shellcheck --color=always --external-sources --shell=bash "$f"
+done