Add helper to track clicks by CSS query

User pass query and we track clicks on high level and send events for matched elements.

API draft is

```js
trackMatchedClicks(plausible, [
  { query: '.header .button-buy', props: { name: 'Buy button', context: 'Header' } },
  { query: '.footer .button-buy', props: { name: 'Buy button', context: 'Footer' } },
  { query: '.content image', props: { name: 'Image click' } },
]);
```