no-js tab switcher

Re: https://stackoverflow.com/a/71008554

```css
dialog { display: block; }

dialog:not(:target):not([open]) { display: none; }
```

```html

Open dialog

Dialog

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Close

```

Not sure if this would have to enumerate every hash target (ex: `#main`, `#settings`) or if this could be done by some sort of dynamic class selector, but this should allow tabs without JavaScript.

No repository file or test is named; start by reviewing the existing boilerplate structure and the CSS/HTML examples in this issue. Determine how the tab targets should be represented, then verify that tabs can switch and close without JavaScript.

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