Update needed packages about insalan.fr

[halfa]

It should, an apt oneliner working at least on debian/ubuntu could be added to the CONTRIBUTING.md. Note: I would rather have composer installed locally instead (from my experience).

[superboum]

In my opinion, feel free to choose the name you prefer, but I think having all installation steps in one place would be beneficial to new contributors, and currently some steps are in README.md. So if you choose to put some information elsewhere, you should also considering migrating or removing the part which is in README.md.

Moreover, a link / reference to where install instructions can be found should be added in the README.md file if you choose to put these information elsewhere, as it is the first thing that you read when you open the github repo.

Generally a CONTRIBUTING.md file does not contain technical information but a Code of Conduct and/or what are the dev processes. Like how you should submit a pull request, etc.

Some times install instructions can be found in an INSTALL.md file, or you can even start a standalone documentation in a doc/ folder with sphinx

And thanks for caring about documentation 👍

[FoxyHawk]

EDIT : Follow up #77, added php-intl extension