Add more details on dyadic transpose

[rodrigogiraoserrao]

The chapter “Working on Data Shape” has a very short introduction about dyadic transpose ⍉ and then goes into some more detail in the specialist's section.

However, neither of the sections about dyadic transpose shows explicitly how the left argument of dyadic transpose can be used to predict the shape of the result.
That is, in no place is this explicitly stated:

shape ← ⍴array
(⍴la⍉array)≡shape[la⍳⍳≢la]

Showing this in code/words could potentially help clarify how dyadic transpose works.