Add Larastan to improve code quality and find possible bugs

[HabuTheTiger]

To improve the code quality and find possible bugs I'd like to implement Larastan.

I think the rule level we can reach could be level 8. To make it easier to review, it might be smart to start at number 1 and create a commit for each level that is fixed (if there are bugs found) until you reach level 8.

Tasks:

• Add Larastan to the project
• Fix any errors that Larastan finds
• Add GitHub action for Larastan