[FEAT] Make `Documentation` main content accessible in keyboard

[coelhucas]

Is your feature request related to a problem? Please describe. In order to #358 make total sense, we have to make an accessible Documentation experience. We also should further discuss how it should work before start working on.

Describe the solution you'd like -> packages/doc/src/components/Documentation/Documentation.jsx We need to improve components from customComponents in order to make them accessible. For instance: we can't navigate through anchors nor interact with the copy button which is only available on hover.

Describe alternatives you've considered The same as described above, but we should consider what to add and change before.