Update readme

[LeoUrzua]

After a review from Bergfeld about how easy it would be as "new eyes" to use it

we got some great feedback from him and here are some things that can be improved

- supports and voteOnAttribute

Explain supports and voteOnAttribute in a detailed way, what is their specific function, and why both exist

Matt's explanation:

This is mostly following the pattern that Symfony started
My thought is that they wanted to separate the concerns of:

• what is this voter concerned with
• does this user have this permission

- Remove unused/confusing code

Remove the unused import { Voter } in the readme example

Voter is a typescript type.

https://github.com/wizeline/access-decision-manager/blame/master/packages/access-decision-manager/README.md#L42

- Add note for developers

Add a note in the access-decision-manger repo for developers.

Since this repo is going to be mainly used for developers with the intention of binding this functionality to different tools like express, react, vue ... etc.

A note saying something like the next text is helpful
“This package is primarily intended to be used by one of the following (list of express / react / vue bindings)”

- Authorization strategies

Add info about the authorization strategies
#23