GOF: Decorator, Extension, Facade

[joaorobson]

Decorator, Extension, Facade GOFs and document it on GitHub pages.

Tasks:

• [x] Study Decorator
• [x] Study Extension
• [x] Study Facade
• [ ] Analyze what we can use in our project

Acceptance Criteria:

• [ ] The document on pages explains what is each one of these GOFs
• [ ] The document explains which ones we can use in our project and why.