Add the Style Guide to the document branch

[VicFalcetta]

Motivation

Closes #28

Modifications

Add a JPEG image that represents our style guide.

Result

There is a style guide that will guide our team

Checklist

This PR is

• [x] In accordance with our coding principles.
• [x] Implementing tests wherever needed and possible.
• [x] Free of commented code.
• [x] Documented.
• [x] Closing an Issue or related to an Issue
• [x] Approved in the CI

[VicFalcetta]

Just to let you know that this is not a major change or anything. It is just the formal addition of the style guide so we can close #28