Implement reusable components

## Expected behavior

Previously defined named components should be available in current code block.

## Example

1.  
    ```razor
    #!blazor --name MyFirstComponent
    <div>
        <h2>This is my first component</h2>
    </div>
    ```

2.
    ```razor
    #!blazor
    <h1>Hello, world!</h1>
    <MyFirstComponent/>
    Welcome to your new app.
    ```