Add a few thing for legal compliance

[ttoine]

This template is at least missing:

• a license.md file (for a template, you can use AFL, like open source modules for PrestaShop)
• in each file, a header with copyright informations (see below)

/**
 * @author    Trenta <contact@trenta.fr>
 * @copyright 2020 Trenta
 * @license   AFL-3.0
*/

You might also want to add in the readme.md that if someone uses this template, they must credit you in an attribution notice (that can be a short text and a link to this repo to put in the readme.md of a module using this template)