Addition of generic / introductory glossary

[thomasgudjonwright]

Closes #117

Please let me know where I missed the mark / could use some review!

[BSnelling]

This glossary is a nice addition to the docs. I think you've covered the key pieces of vocabulary and it will be useful to have them summarised conveniently in one place.

Will this glossary be its own page in the docs? In which case, you'll need to modify docs/make.jl once you know where you want it to go.

[BSnelling]

Is the adjoint always the conjugate transpose of the Jacobian specifically? In the below definitions which reference the adjoint, it's always the "adjoint of the Jacobian".

This makes me think the adjoint definition should be "The conjugate transpose of a matrix" and the subsequent definitions can refer to "the adjoint of the Jacobian".

Alternatively if, when we mention the adjoint, we're always talking about the adjoint of a Jacobian, this definition can stay as it is and in subsequent definitions we can just say "the adjoint".

[oxinabox]

Probably we want to title the Adjoint of a function.
ANd start by saying that the adjoint of a matrix is another word for it's conjugate transpose.
Then mentioning that it can also be applied to a linear operator as every linear operator can be described as y = Jx and that as an adjoint linear operator of y' = x'J'.
Then say that people say as a shorthand/abuse of terminoly the adjoint of a function,
when what they actually mean is to get a function which is the adjoint of pushfoward linear operator.
The pushforward linear operator is the the linear operator that has the same jacobian as the function at that point.
The pullback is its adjoint.
linearization of the function at a point, to get a linear operator (the pushforward),
and then
Then say that people occationally say the adjoint of a function,
when what they really mean is: the adjoint of the jacobian of the function,
or they mean the pullback.
Sometimes people say adjoint of a function to mean pullback.

[thomasgudjonwright]

I totally agree this def isn't sufficient. The adjoint is super broad as a term, so I am having a hard time figuring out how much / how little to include

[oxinabox]

this sentence is unclear

[thomasgudjonwright]

Updated with more fundamental info

[oxinabox]

Nice work Tom.
Sorry it has taken so long to review it.

Thing that would really polish this would be to have cross reference links within this page for when things refer to other things.
Or really next level if we can do it across the whole of the docs for each time something is mentioned.

Also would be nice to link to wikipedia in a few things.