Write documentation about customization

[coderdiaz]

Currently, we do not have documentation on how people can modify and customize the project to make the template fit their needs.

Considerations:

• A more detailed structure of the project.
• Technologies and how they work.
• Which files are important to customize the website.
• How SEO was implemented.

If you detect any other important information, feel free to add.

[google-labs-jules]

View task progress at https://jules.google.com/task/9751264945378702376