Update README.md | Add exmaple for executing external program in Node

Author: JiaEnChua

README.md

@@ -300,7 +300,11 @@ req.end()
 
 ## Q. ***How to execute an external program from within Node.js?***
 
-*ToDo*
+const { exec } = require('child_process');
+
+exec('"/path/to/test file/test.sh" arg1 arg2');
+
+exec('echo "The \\$HOME variable is $HOME"');
 
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