[DOC] Set up documentation.

[Ángel Gómez]

Summary: The documentation is a very important part of the development of software. The main purpose of this issue is to set up all the documentation resources. Those are:

• README.md
• Markdown documentation
• Latex documentation
• Spell checking

Relates to:

• #39

Acceptance criteria:

• There is a doc folder that contains all the documentation related to the software and the TFM.
• The CI is configured to check the spelling of the documentation.