Replace styleci with php-cs-fixer

[usu]

I'd suggest we replace styleci with php-cs-fixer to make it easier for auto-formatting during local development

Similar as done in FOSHttpCache in commit FriendsOfSymfony/FOSHttpCache@944b859

[dbu]

yes, i agree. i also think php-cs-fixer is more up to date with rules.

do you want to do the MR for this? after merging, i will remove the styleci hook

[usu]

Yeah, I can do a PR for this. I suggest we try to merge #622 and #618 beforehand to avoid too many merge conflicts

[dbu]

fixed in #626