Improve shop creator with phpstan

[mflasquin]

Questions	Answers
Description?	Improve shop creator with phpstan
Type?	improvement
BC breaks?	no
Deprecations?	no
Fixed ticket?	Fixes #23
How to test?	see https://github.com/mflasquin/prestashop-shop-creator/pull/4
Possible impacts?	Please indicate what parts of the software we need to check to make sure everything is alright.

[mflasquin]

POC CI : https://github.com/mflasquin/prestashop-shop-creator/pull/4

[mflasquin]

PR is ok but needs to be rebased to fix git conflicts

Please rebase and ping me and then I will approve ;)

Hi @matks, done :smile:

[matks]

Thank you @mflasquin