Add documentation

[matyo91]

Hello,

As I can likely understand terms as Applicative, Functor, SemiGroup which are mathematical terms we can found on schema https://en.wikipedia.org/wiki/Monoid

I don't understand what are all terms and specially what is Brand and HK1.
So may be adding some documentation about mathematical terms on the project should help people understands the theorical concepts.

[marcosh]

There's also issue #7 regarding documentation

For the moment, the best reference for understanding the concepts is my blog.
In particular, regarding branded types and higher kinded types, you can take a look at
http://marcosh.github.io/post/2020/04/15/higher-kinded-types-php-issue.html and http://marcosh.github.io/post/2020/04/15/higher-kinded-types-php-solution.html

[matyo91]

Thanks. So I close the issue as there is already one open and as the issue will stay referenced to #7 !