Implement merge sort

[mahimagoyalx]

Merge sort is missing in the sorting section, I would like to add it as a part of Hacktoberfest.

[mahimagoyalx]

@akshitagupta15june Please assign it to me and add hacktoberfest label.

[akshitagupta15june]

@mahimagoyalx yup please add!!

[mahimagoyalx]

Could you please assign it to me and add the hacktoberfest label as well? @akshitagupta15june

[akshitagupta15june]

@mahimagoyalx you can fork the repo and raise a pull request after adding the code in sorting repo of CPP. I will merge it.

[mahimagoyalx]

@akshitagupta15june Sure!

[07-Atharv]

@akshitagupta15june can you assign these task to me??