docs: add explanations for Serverless, Members, and Special layers in…

[aarya0044]

Issue

The current Landscape Guide diagram includes a "Serverless" column, a "Members" column, and a bottom-most layer labeled "Special", but there is no accompanying explanation in the documentation.

Since these elements are part of the official diagram, adding descriptions for them would improve clarity, completeness, and usability — especially for new contributors trying to understand the architecture.

Proposed Changes

• Add a short explanation for the Serverless column (purpose and examples)
• Add a short explanation for the Members column (who it represents and role)
• Add a section describing the Special layer (why it exists, what it includes, and how it differs from other layers)

Benefits

• Makes documentation more complete
• Helps contributors better understand architecture
• Improves onboarding for beginners
• Avoids confusion and assumptions about undocumented sections

Let me know if you'd like me to format the content in a specific style to match the repo.

[aarya0044]

Hi maintainers 👋
This PR only adds documentation for missing architecture layers.
No changes were made to the .github/workflows/ directory or landscape.yml.
The "Validate landscape.yml" workflow is currently awaiting approval — could you please approve the workflows to run?
Thanks a lot for your support!