Babel Macro

It would be nice to have a babel macro that automatically runs the babel plugin to remove the runtime. That way, this project would work out of the box with "zero" config tools like create-react-app.

I'm thinking it could be something like:
```js
import {html} from 'htm/preact/macro'
```

This is similar conceptually to CSS-IN-JS libraries providing a macro for their tools. See https://emotion.sh/docs/babel-macros

Start by reading the existing Babel plugin and the Babel Macros documentation linked in the issue, then compare the proposed htm/preact/macro import with the create-react-app zero-config constraint. Done means the requested macro entry point works with that setup and its behavior is verified against the existing plugin; the issue does not name repository files or tests.

索引モデルが issue の本文から書いたものです。