GOF: Abstract and Singleton

[gabibguedes]

Study Abstract and Builder GOFs and document it on github pages.

Tasks:

• [ ] Study Abstract
• [ ] Study Singleton
• [ ] 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 wich ones we can use in our project and why.