add identity core to blazor code example

Example 1: blazor sample ujsing cliam policy

[Route("api/[controller]")]
[ApiController]
public class SystemController 
{
    [Authorize(Policy = “IsDeveloper”)]
    public IActionResult LoadDebugInfo()
    {
        // ...
    }
}

Example 2: blazor sample ujsing cliam policy

<AuthorizeView Policy="IsDeveloper">
    <p>You can only see this if you satisfy the IsDeveloper policy.</p>
</AuthorizeView>