Add README for RootNamespaceTest sample

Co-authored-by: Soar360 <[email protected]>

Author: Copilot

samples/RootNamespaceTest/README.md

@@ -0,0 +1,55 @@
+# RootNamespace Test Sample
+
+This sample project demonstrates and validates that the source generator correctly respects the `RootNamespace` property in the .csproj file.
+
+## Purpose
+
+When a project sets `<RootNamespace>Popcorn.Toolkit</RootNamespace>` in its .csproj file, the generated `R` class should be placed in the `Popcorn.Toolkit` namespace rather than defaulting to the assembly name.
+
+## Project Configuration
+
+The project is configured with:
+- **AssemblyName**: RootNamespaceTest
+- **RootNamespace**: Popcorn.Toolkit
+- **Resources**: Contains sample.txt and config.json
+
+## Expected Behavior
+
+The source generator should:
+1. Read the `RootNamespace` property from MSBuild
+2. Generate the `R` class in the `Popcorn.Toolkit` namespace
+3. The Program.cs can access `R` class directly since it's in the same namespace
+
+## Running the Test
+
+```bash
+dotnet run --project samples/RootNamespaceTest/RootNamespaceTest.csproj
+```
+
+Expected output:
+```
+RootNamespace Test - Verifying generated R class namespace
+=============================================================
+
+R class is accessible in namespace: Popcorn.Toolkit
+Expected namespace: Popcorn.Toolkit
+
+Available resource keys:
+  - R.Keys.sample: sample
+  - R.Keys.config: config
+
+Sample resource content: This is a sample resource file for testing RootNamespace property.
+Config resource content: {
+  "message": "Hello from RootNamespace test!",
+  "version": "1.0"
+}
+
+✓ Test PASSED: R class is in the correct namespace (Popcorn.Toolkit)
+```
+
+## Verification
+
+The test program:
+1. Accesses the `R` class without qualification (proving it's in `Popcorn.Toolkit`)
+2. Verifies the namespace using reflection
+3. Reads resources to ensure functionality works correctly