Merge sort

[ShivamGoyal03]

Merge sort code is missing, I can write both code in CPP and java.

[mvaja13]

Can you assign this to me?

[abhijeet8800]

i would like to work on this project @Shivam-090. Can you please assign it to me.

[gdscucer]

Can you assign this to me?

raise the issue

[roushan-rks]

Can you assign this to me? @gdscucer

[Arika008]

@gautamV19 Please check my PR #94