Graph docs lack a beginner-friendly introduction explaining Spatial Graph.

[snehaseveriya23]

The current Graph documentation starts with a migration guide but does not clearly explain what a Spatial Graph is or how it relates to spatial weights.

As a beginner user, it is unclear whether Graph is intended as a replacement for weights (W) or an alternative abstraction. The intro page
(docs/user-guide/graph/intro.rst) currently acts only as an index and does not provide a conceptual overview.

I propose adding a short introductory section that:

• Defines what a Spatial Graph is
• Clarifies its relationship to spatial weights
• Directs users to the migration guide for details

This would improve understanding for new users transitioning from weights.

[martinfleis]

See #854

[snehaseveriya23]

Thanks for the pointer! I’ve checked #854 and see that it already adds a broader introductory notebook and updates to the Graph docs.

My PR only adds a small textual intro in 'intro.rst' to clarify what a Spatial Graph is for beginners. Happy to close this issue or defer to #854 if that’s preferred.