new lesson: Merge Sort

[Utkarsh1504]

⭐ Request Type

Add in-depth documentation for the lesson Merge Sort.
you can start your contribution from this file

Lesson Content

The lesson must contain at least these are the topics:

1. Introduction
2. Understanding the merge sort
3. implementation + illustration
4. code for merge sort
5. complexity analysis+stability
6. applications

💻 Location

location of the file is at:
section: 8
lesson: E
order: 8E
filename: mergesort.md

❌ Additional Info

You can take the help of other markdown files in the /lesson directory so that you get the idea of in which fashion you should write.

If you don't know how to do markdown, don't worry it is quite easy, just follow this docs-https://guides.github.com/features/mastering-markdown/

[Shaurya-21]

please assign this issue

[Vi-r-us]

Can you assign this issue to me.

[shubhamSM1298]

Can you assign this issue to me.