Add an example for the feature editable packages

[uilianries]

Possible references:

https://docs.conan.io/en/latest/developing_packages/editable_packages.html https://docs.conan.io/en/latest/reference/config_files/editable_layout.html https://docs.conan.io/en/latest/reference/commands/development/editable.html

Deprecated, it uses conan link https://blog.conan.io/2019/02/04/New-conan-release-1-12.html

https://blog.conan.io/2019/03/12/New-conan-release-1-13.html

Well, I have no power to attribute myself, but I would like to do it.