Page prediction with multiple profile/strategy

> [**📚 References**](https://developer.mozilla.org/en-US/docs/Glossary/Page_prediction)
> see [instant.page](https://instant.page/tech) and [quicklink](https://github.com/GoogleChromeLabs/quicklink#how-it-works)

Attribute values: (the attribute name still not decided)
- [ ] `!smart` = prefetch page on [pointerenter][] then preload all resources (css, js) on [pointerdown][]
- [ ] `!conservative` = prefetch page (+ css-in-header) on [pointerdown][]
- [ ] `!aggresive` = prefetch page when [link](12) is [visible][] then preload all resources (css, js, image?🤔) on [pointerdown][]

[pointerenter]: https://developer.mozilla.org/en-US/docs/Web/API/Element/pointerenter_event
[pointerdown]: https://developer.mozilla.org/en-US/docs/Web/API/Element/pointerdown_event
[visible]: https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API#how_intersection_is_calculated