adding back sh file into external

external/bioptim_install_windows.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+## Move to the external folder
+cd ${0%/*}
+
+git submodule update --recursive --init
+
+## Move to the bioptim folder
+cd bioptim
+
+# Installing bioptim
+python setup.py install