Add a few standard problems solved using monotonic stack

[LakshaySK106]

Objective: Create a new directory "Stack" and inside it create a new folder respective to your programming language. Add all your codes to this folder.

[Ashish-242]

Hey Can you assign me this issue as stack is my faviourite data structure i can do this?

[LakshaySK106]

You're assigned @Ashish-242

[adripo]

@LakshaySK106 I updated my PR with more examples in Python. I also removed the readme files.