Add ForgeMap to Object to object mapping

[superyyrrzz]

Add ForgeMap to the Object to object mapping section.

ForgeMap is a Roslyn incremental source generator that generates object mapping code at compile time. It differs from existing entries:

• vs AutoMapper: Compile-time code generation instead of runtime reflection. MIT licensed (AutoMapper went commercial in v15+).
• vs Mapperly: Similar source generator approach but with a different API — uses partial class with method signatures rather than attribute-decorated mapper classes. Supports ForgeInto (map into existing objects), ReverseForge, BeforeForge/AfterForge hooks, and per-property ConvertWith.
• vs Mapster: Compile-time only, no runtime fallback. Lighter dependency footprint.

The project is actively maintained (v1.6.0), has tests, documentation, and is published on NuGet.