Update README and add gitlab-ci.yml

@Grevil I think this should be split into 2 tasks, so the chance to get it fixed is higher. Or will you do both now that you're on it?

Already updated the module page! Please review!

PHPStan is unhappy:

 ------ ---------------------------------------------------------------------- 
  Line   src/FileToMedia.php                                                   
 ------ ---------------------------------------------------------------------- 
  71     \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  73     \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  107    \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  149    \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  156    \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  183    \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
  192    \Drupal calls should be avoided in classes, use dependency injection  
         instead                                                               
 ------ ----------------------------------------------------------------------

You don't have to fix this for me, just FYI.

LGTM & RTBC afterwards. Left just 1 comment. Thank you, wonderful work :)

All fixed!

Automatically closed - issue fixed for 2 weeks with no activity.