Added mas check to App Store install script

Necessary to ensure mas is installed before executing the script. This
reduces the strain on downstream projects/scripts from having to do
this check. This was previously part of the macOS Configuration project
but has been moved here as central location for core functionality.

bin/install_app_store

@@ -9,6 +9,7 @@ IFS=$'\n\t'
 SCRIPT_PATH="$MAC_OS_CONFIG_PATH/bin/install_app_store"
 
 if [[ -x "$SCRIPT_PATH" ]]; then
+  check_mas_install
   "$SCRIPT_PATH"
 else
   printf "WARNING: App Store install script does not exist or is not executable.\n"