TIL about the "popover API" in #html

With this you can have fully declarative modals with zero js.

```
<button popovertarget="mypopover" popovertargetaction="show">
Show popover
</button>
<button popovertarget="mypopover" popovertargetaction="hide">
Hide popover
</button>
<div id="mypopover" popover>Popover content</div>
```

https://developer.mozilla.org/en-US/docs/Web/API/Popover_API/Using