Container component for App Home surface

[yhatt]

Today Slack introduced "App Home", the new Block Kit surface for the interaction between Slack app and user.
https://api.slack.com/reference/app-home

An usage of Block Kit for App Home is not so different from message. User still can compose contents for App Home by using jsx-slack's <Blocks> container.

So why should we create container component? Now the official document of layout blocks are sorted to show the supported blocks in each surfaces. Providing <Home> container component, with check valid blocks strictly (like #64), is better for composing correct blocks suitable with each view.