Add Grin provider (#436)

Author: Astronautandall

providers.csv

@@ -20,3 +20,4 @@ VOI,1f129e3f-158f-4df5-af9c-a80de238e334,https://www.voiscooters.com/,https://md
 MOVO,40dad54c-e199-4fd8-9f5b-cff93ffced63,https://movo.me,https://mds.movo.me,https://gbfs.movo.me
 Baus,638ba503-4006-4c53-bf34-cd625cc03d61,https://bausmoves.com,https://mds.bird.co,https://mds.bird.co/gbfs/platform-partner/v2/baus
 Bolt Technology,7ea695ca-9de7-4b3b-9f3c-241b2045a1fe,https://bolt.eu,https://mds.bolt.eu,https://mds.bolt.eu/gbfs/1
+Grin,8a0ecfce-5fb3-451e-8069-434b79c8b01a,https://ongrin.com,https://open-data.grow.mobi/mds/,https://open-data.grow.mobi/api/v1/gbfs/