Sets in Python

[Raksha001]

1. This pull request resolves #106

2. Description

In this tutorial, I have added 3 files under the sets folder explaining how sets are created, adding or removing elements from the sets with challenges.

3. Fill in checklist by marking [x]

• [x] I've read the CONTRIBUTING.md
• [x] I was assigned to this issue
• [x] My code is formatted using required linting
• [x] I've run my code locally and checked it works

[sabderemane]

Due to a large amount of reviews, I put the label Hacktoberfest-accepted but the review will be done later