Update README.md

Author: gouravthakur39

README.md

@@ -57,6 +57,7 @@ These program are written in codeblocks ide for windows. These programs are not
 - [Swap By Reference Vs Swap By Copy](https://github.com/gouravthakur39/beginners-C-program-examples/blob/master/SwapByRefandCopy.c)
 - [Display Linux Environment Variables](https://github.com/gouravthakur39/beginners-C-program-examples/blob/master/DisplayLinuxEnvirmentVariables.c)
 - [Factorial](https://github.com/gouravthakur39/beginners-C-program-examples/blob/master/Factorial.c)
+- [Get String Length](https://github.com/gouravthakur39/beginners-C-program-examples/blob/master/StringLength.c)