Add README documentation for wasmbrowser template

Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Author: Copilot

src/mono/wasm/templates/templates/browser/README.md

@@ -0,0 +1,62 @@
+# WebAssembly Browser App Template
+
+This template creates a .NET app that runs on WebAssembly in a browser.
+
+## Template Options
+
+### UseMonoRuntime
+
+**Parameter:** `--UseMonoRuntime`  
+**Type:** boolean  
+**Default:** `true`
+
+Determines whether to use the Mono runtime for WebAssembly.
+
+When set to `true`, the generated project file will include:
+```xml
+<UseMonoRuntime>true</UseMonoRuntime>
+```
+
+#### Usage Examples
+
+Create a project with Mono runtime (default):
+```bash
+dotnet new wasmbrowser -n MyApp
+```
+
+Or explicitly specify:
+```bash
+dotnet new wasmbrowser -n MyApp --UseMonoRuntime true
+```
+
+Create a project without the Mono runtime property:
+```bash
+dotnet new wasmbrowser -n MyApp --UseMonoRuntime false
+```
+
+## Getting Started
+
+After creating your project:
+
+1. Navigate to your project directory:
+   ```bash
+   cd MyApp
+   ```
+
+2. Run the application:
+   ```bash
+   dotnet run
+   ```
+
+3. Open your browser to the URL displayed in the console output (typically `https://localhost:7000` or `http://localhost:5000`).
+
+## Project Structure
+
+- **Program.cs** - The entry point of your application
+- **wwwroot/** - Static web assets (HTML, CSS, JavaScript)
+- **Properties/** - Project properties and configuration
+
+## Learn More
+
+- [.NET WebAssembly Documentation](https://learn.microsoft.com/en-us/aspnet/core/blazor/webassembly)
+- [Mono Runtime](https://www.mono-project.com/)