Add detailed instructions for generating .struct.yaml files

[httpdss]

Issue

Description

This PR enhances the documentation by providing comprehensive guidelines for creating .struct.yaml files. The main feature is the update to the docs, which now include:

• Detailed instructions for defining structures, folders, and variables
• Examples for file and folder definitions
• Important notes and conventions for using the STRUCT tool
• References to the STRUCT schema, README, and available contribs

These improvements make it easier for users to understand and correctly use the STRUCT tool for project scaffolding.

Checklist

• I have read the contributing guidelines.
• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have updated the documentation accordingly.

Screenshots (if applicable)

Additional Comments

• The main feature is the improved documentation for .struct.yaml file generation.