Add Data Spaces: Fundamentals & Deployment documentation and update n…

[sermars]

This pull request introduces a comprehensive new documentation page focused on the fundamentals and deployment of data spaces using Fiware technology. It aims to provide a clear technical introduction for newcomers and offers practical guidance and resources for deploying and understanding data spaces. The new page is also integrated into the site's navigation for easier access.

Documentation additions and improvements:

• Added a new page, fundaments_deployment.md, covering key concepts, recommended prerequisites (Kubernetes, Helm), and curated external resources (official documents, webinars, and smart data models) to help users understand data spaces and their technical foundations.
• Included detailed step-by-step instructions for deploying a data space locally using either the official Fiware deployment or a recommended minimum viable data space example, with links to example environments and advanced tips.
• Provided additional resources, including YouTube webinars on decentralized IAM and contract negotiation in data spaces, to deepen understanding of advanced topics.

Navigation update:

• Added the new "Fundamentals & Deployment" documentation page to the navigation under "Data spaces" for improved discoverability.