Add linear regression

[Shradha27]

Description

Added a file named "Linear_regression.py" that implements Linear Regression algorithm in Python.

Related Issue

https://github.com/Asiatik/codezilla/issues/382

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• [ ] Bug fix (change which fixes an issue with the algorithm)

• [x] New Algorithm (non-breaking change which adds functionality)

• [ ] Documentation

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

If you're unsure about any of these, don't hesitate to ask. We're here to help!

• [x] My code follows the code style of this project.

• [ ] My change requires a change to the documentation.

• [x] I have updated the documentation accordingly.

• [x] I have read the CONTRIBUTING document.