flutter_package / fluttertpc_get

[docs] several changes in docs

Add util extensions again in the lib + add missing function

[docs] fix typos

Update link for state management explanation

[docs] more docs for dependency management

Update README-es.md

 adding function to validate cpf isCpf

get_instance.dart redundant ternary

The ternary on the line ~222 it is a redundant ternary. Another possibility would be if the key is not null print it, instead of $ newKey