Add header, footer, and basic page layout

[ademarco]

We need to enhance the ILO Drupal base theme by adding key structural elements and basic layout components. Specifically, we will:

• Add a Header and Footer, using components from the ILO Design System. These components are exposed as UI Patterns.
• Style the main menu by integrating it into the header component.
• Provide a basic page layout, including styling for elements such as the page title and any necessary page wrappers.