Improve CONTRIBUTING.md

[silviodc]

What is the problem?
Many people have doubts about how to install Serenata and download the data using the toolbox.

How can this be addressed?
We can create a short video (no more than 10 minutes) explaining step by step the following points:

1. Clone the project from git
2. Install Serenata using Docker
3. Necessary configurations
4. Download the data using the toolbox in a Jupyter notebook.

Who could help with this issue?
Anyone really

Labels
Documentation, hacktoberfest

Important
It's not possible to embed videos directly, but we can put an image which links to a youtube video:
[![IMAGE ALT TEXT HERE](http://img.youtube.com/vi/YOUTUBE_VIDEO_ID_HERE/0.jpg)](http://www.youtube.com/watch?v=YOUTUBE_VIDEO_ID_HERE)

[JorgeMadson]

I would really apreciate it (a video explaing step by step)! I tryied to run it but it didn't.

[anaschwendler]

Hi everyone!

I recorded a video to show how to install the project without Docker, but I'm not explaning anything,
but I show where is the datasets and how to create a new notebook.

I'll release the a version with Docker soon, just collecting some feedback

https://youtu.be/g9hmMFVp4rs

[anaschwendler]

Now the installation with Docker: https://youtu.be/3XwvZbCvZKQ

🎉