Document EF.Functions.JsonContains()

[roji]

See dotnet/efcore#37566

[Copilot]

Pull request overview

This PR adds documentation for the new EF.Functions.JsonContains() method introduced in EF Core 11.0, which provides direct access to SQL Server's JSON_CONTAINS function for advanced JSON querying scenarios.

Changes:

• Updates the section title to "Contains operations using JSON_CONTAINS" to better reflect both automatic and manual usage
• Adds a new subsection documenting EF.Functions.JsonContains() with code examples and SQL output
• Adds an entry to the SQL Server functions mapping table

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
entity-framework/core/what-is-new/ef-core-11.0/whatsnew.md	Generalizes section title and adds new subsection documenting manual usage of JsonContains function with code examples
entity-framework/core/providers/sql-server/functions.md	Adds JSON functions section with JsonContains mapping entry