Update README and contributing docs for multitenancy

Added shipped status and getting started instructions for the Multitenancy core extension in the README. Updated documentation links to use Markdown format and clarified link formatting guidelines in the contributing guide.

Author: mheidari988

README.md

@@ -20,9 +20,12 @@ Quick links:
 ## Status
 
 - Shipped: `CleanArchitecture.Extensions.Caching` (net10.0)
-- Planned: Multitenancy core and adapters
+- Shipped: `CleanArchitecture.Extensions.Multitenancy` (core, host-agnostic, net10.0)
+- Planned: Multitenancy adapters (AspNetCore, EFCore, Identity, Provisioning, Redis, Sharding, Storage)
 
-## Getting started (caching)
+## Getting started
+
+### Caching
 
 1. Install:
    ```powershell
@@ -36,11 +39,29 @@ Quick links:
 3. Configure caching options as needed.
 4. No other template changes required.
 
+### Multitenancy core
+
+1. Install:
+   ```powershell
+   dotnet add src/Application/Application.csproj package CleanArchitecture.Extensions.Multitenancy
+   dotnet add src/Infrastructure/Infrastructure.csproj package CleanArchitecture.Extensions.Multitenancy
+   ```
+2. Register:
+   ```csharp
+   services.AddCleanArchitectureMultitenancy();
+   ```
+3. Resolve tenants in your host and set the current context (host adapter required).
+4. Add pipeline behaviors:
+   ```csharp
+   services.AddMediatR(cfg => cfg.AddCleanArchitectureMultitenancyPipeline());
+   ```
+
 Docs to read next:
 
-- Caching overview: https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/extensions/caching/
-- Extensions catalog: https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/extensions/
-- Roadmap: https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/roadmap/
+- [Caching overview](https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/extensions/caching/)
+- [Multitenancy core overview](https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/extensions/multitenancy-core/)
+- [Extensions catalog](https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/extensions/)
+- [Roadmap](https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/roadmap/)
 
 ## Repo layout
 

docs/contributing/index.md

@@ -27,3 +27,4 @@ We keep the upstream Jason Taylor template pristine and ship everything as opt-i
 - Use fenced code blocks with language tags (`bash`, `powershell`, `csharp`, `json`).
 - Prefer snippets from source to avoid drift; keep examples short and runnable.
 - Keep compatibility info current (template version, target frameworks, dependencies).
+- Format external links as Markdown links, for example `- [Roadmap](https://cleanarchitecture-extensions.github.io/CleanArchitecture.Extensions/roadmap/)` (avoid `Label: URL`).