Missing Contribution.md file

[yaarAdarsh]

There is a need to add a contribution.md file. So that anyone who wants to contribute have an idea of what steps to follow for contribution. I want to work on this issue. Please assign me this task.

[diptanu]

@yaarAdarsh Feel free to work on it. Generally

Server

1. Write tests
2. Run the graph_behaviours.py integration tests
3. Write a test plan of how they tested the features.

[yaarAdarsh]

@diptanu please review my PR / merge it.