Add DFN-6 package definition for TSL2591

Footprint: kicad-footprints!3387 (merged)

Symbol: kicad-symbols!4158 (merged)

Datasheet: https://ams.com/documents/20143/9331680/TSL2591_DS000338_7-00.pdf

Not sure if it should go to the DFN package directory or create a new more custom like Sensor_Optical.pretty .