feat: add Dart mod

[devhammed]

This pull request adds support for Dart.

[sgimenez]

I don't know much about Dart, but would it not be possible to have a main() function in the robot.dart file that calls start() and a laby_name_ant() that is defined in the skel file like it was done in C (and other languages)?

[devhammed]

@sgimenez I have updated the mod structure to match your specifications but it requires creating an empty program.dart file in the lib folder to bypass the Dart's compiler function is not defined: laby_name_ant error while developing.

PS: I still think my former structure is more compact because it does not require hacks.