Issue #3408122: Add gitlab CI
Closes #3408122
Added a phpstan.neon
config file for phpstan.
Level has been set to the lowest value (1). Feel free to up the value when errors/warnings for this value have been fixed.
The most important setting is that we are now ignoring warnings like "Unsafe usage of new static" since new static() is a best practice in Drupal, we cannot fix that.