Add a "Sharp Bits" page to docs

[adrn]

From helping @rrubenza with some conceptual sticking points with unxt, it occurred to me that it would be useful to have a "Sharp Bits" page for unxt -- right now the quaxify/jax function discussion is down in the "getting started" but really could be a larger block in a "sharp bits" page.

[nstarman]

Agreed. More worked example.