i want to add the code of -> find greatest common divisor (GCD)

[GautamGoyal2341]

The code of GCD is missing it is basic cpp practice code

[RishabhSharma96]

@gdscucer
please assign it to me

[GautamGoyal2341]

@gdscucer misclicked , i am writing the code assigned to me again code is ready with proper comments

[Saurabhk1975]

assign me I want to work on this @gdscucer

[Arika008]

@gdscucer Please check my PR #93