No build tools route debugging

I've started developing using the stand-alone module from `https://unpkg.com/htm/preact/standalone.module.js` but realize that I really need the debugging tools.

The [documentation](https://preactjs.com/guide/v10/debugging#installation) says to `import "preact/debug"`, but that's not a valid module specifier. There doesn't seem to be a debug standalone bundle on unpkg.

So alternatively, I might be able to adapt the following example code:
```js
import { h, Component, render } from 'https://unpkg.com/preact?module';
import htm from 'https://unpkg.com/htm?module';

const html = htm.bind(h);
```

`https://unpkg.com/preact/debug?module` is not a thing, but the package [preact/debug/dist/debug.module.js](https://unpkg.com/browse/preact@10.5.5/debug/dist/debug.module.js) looks promising. However, it starts of with `import "preact";`, which doesn't work.

So my question is, is there a way to use and debug Preact + HTM without build tools?

If so, I'd love to make a PR for the docs.

Start with the debugging installation documentation and the standalone.module.js, preact?module, and preact/debug/dist/debug.module.js URLs mentioned in the issue. Verify whether Preact and HTM debugging can work without build tools; done means documenting a confirmed no-build setup or clearly documenting that none is supported.

Scritto dal modello di indicizzazione a partire dal testo della issue.