Add docs page on deriving array rules (#191)

* Add first draft

* Remove newlines before and after dollars

* Add whitespace

* Fix note

* Add more comparison at the top

* Add explicit type

* Apply suggestions from code review

Co-authored-by: willtebbutt <wt0881@my.bristol.ac.uk>

* Change title

* Clarify that this is notational

* Standardize headers

* Use tilde for spacing

* Clarify Frobenius inner product

* Make equations more readable

* Fix formatting and add missing character

* Reference Julia functions more clearly

* Link to functions

* Wrap long equations

* Add julia functions and more steps

* Wrap long equation

* Use conj notation

* Swap order

* Add frules

* Use real instead of Re

* Clean up frule formatting

* Elaborate for matrix inverse

* ChainRules notation

* Annotate steps and use eq refs

* Keep equations within 92 chars

* Use footnote

* Add more identities

* Bye Frobenius

* Clean up language, add spacing

* Apply suggestions from code review

Co-authored-by: Nick Robinson <npr251@gmail.com>

* Simplify header

* Clarify goal in introduction

* Rewrite forward-mode section

* Reqrite intro

* Simplify equations, and rewrite

* Rewrite reverse mode example

* Fix typos and clean-up

* Change link text

* Generalize header

* Clarify language

* Fix incorrect variable name

* Add missing space

* Run code through formatter

* Add logabsdet example

* Add note on complex circle

* Move the note lower

* Pullback to adjoint

Co-authored-by: willtebbutt <wt0881@my.bristol.ac.uk>
Co-authored-by: Nick Robinson <npr251@gmail.com>

Author: 3 people

docs/make.jl

@@ -29,6 +29,7 @@ makedocs(
         "FAQ" => "FAQ.md",
         "Writing Good Rules" => "writing_good_rules.md",
         "Complex Numbers" => "complex.md",
+        "Deriving Array Rules" => "arrays.md",
         "Debug Mode" => "debug_mode.md",
         "Design" => [
             "Many Differential Types" => "design/many_differentials.md",