[Tooltip] Raw implementation with vanilla JS

[JeremiePat]

This is the tracking bug for implementing accessible tooltips using only raw web technologies available in browsers.

We need to :

• [ ] Document dialog boxes requirements and usage (in English)
• [ ] Document dialog boxes requirements and usage (in French)
• [ ] Define functional specifications as Gerkins tests
• [ ] Implement a first version of those specification
• [ ] Formally tests those specifications

[JeremiePat]

According to ARIA best-practices, the normative expectation around that component are not yet settled:

• https://w3c.github.io/aria-practices/#tooltip
• https://github.com/w3c/aria-practices/issues/128

Because of that, that issue won' block any milestone we want to reach.