[Docs] Improve Documentation for Sharing Functionality

[zihanKuang]

The current "Sharing Designs" doc is too brief and UI-focused. It lacks explanation of background concepts, usage scenarios, and advanced behaviors. Key issues:

1. Too Simplified: Only describes clicking "Share" without explaining when or why to share, or how sharing works in real cases.
2. Missing Team Scenarios: No guidance on how designs inside a workspace become accessible to teams, or how team-level permissions work.
3. No Visuals: No screenshots or diagrams. This makes it hard to follow.
4. No Cross-Links: Doesn’t link to related pages like Workspace docs or Catalog.
5. Structure Suggestion: Add a new section on "Sharing with Teams", or create a separate page like "Granting Access for Teams" and link from here.