add style target to makefile

[johko]

Added the style target to the makefile, so you actually can run make style to fix formatting.
(command shamelessly copied from the audio course https://github.com/huggingface/audio-transformers-course/blob/main/Makefile )

[jungnerd]

I've reviewed it. Please check it out 🤗

[mmhamdy]

Looks good! @jungnerd has already noted most of the comments. Thanks @johko

[johko]

Thanks for the suggestions @jungnerd, both make sense to me 🤗

[merveenoyan]

Thanks!