P: Add Grain slider to local adjustment controls

Hi,

I work a lot in lightroom, and often look to reproduce filmic vibes to my photos. When adding grain to a photo, it renders across the whole image and this is unrealstic. We would see less or no grain found in the highlights compared to the shadows. I would love to be able to add grain through a luminosity mask, where I could control the amount and make more realistic eidts.