Add extern file check for fillit

[Seluj78]

https://github.com/jgigault/42FileChecker/blob/cf6a18a446f13850962031b7ca8c00ecdecabee7/includes/projects/fillit/fillit_main.sh#L111-L177

[Seluj78]

I just checked the pdf. The extern files aren't limited anymore. no need to check for that.