Rework documentation

[NelsonVides]

Based on feedback from this threat in the Erlang Forums, I thought of entirely reworking the documentation. I was never really a big fan of that large README file with everything, never found it much readable and most of my knowledge of the library really came from how we use it in MongooseIM. So I decided to split that big readme and move most of it to the respective types and function definitions defined in the wpool module, taking care of all the links working right. That also puts documentation next to the code, which might be easier to maintain in the future.

The best way to review this would be to build docs locally with rebar3 ex_doc and browse :)

I also added a function that creates the child-spec directly, so that it can be added to a supervision tree.

It is on top of the commit added to #198 for convenience for me mostly, so merging that one first would be best :)

Now, for the documentation to build correctly and display all the information in the defined types, we really need to let rebar3_format allow comments directly below types, as this is how ex_doc builds docs for types :|

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9ddf1aa) 92.54% compared to head (223450a) 92.57%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #200      +/-   ##
==========================================
+ Coverage   92.54%   92.57%   +0.03%     
==========================================
  Files          10       10              
  Lines         456      458       +2     
==========================================
+ Hits          422      424       +2     
  Misses         34       34              

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[NelsonVides]

Lovely to see this merged! Wanna publish a new package @elbrujohalcon to have the docs public? 😁

[elbrujohalcon]

Done already. https://hexdocs.pm/worker_pool/readme.html