If something’s stirring in Jersey City’s hip-hop scene, there’s a good chance Junestar Mr. Blackman will be involved. The Chilltown OG has earned kudos as a singer, songwriter, musician and producer, but behind the scenes, he’s equally renowned as a community activist and mentor. This weekend, he’ll perform in the city twice, first at a pop-up showcase at Ript Dispensary on Friday, May 3, and then on Saturday, May 4, at “We the People, Vol. II: Vox Populi,” a benefit for Moore’s Lounge at the Samuel R. Shelton VFW Post 229. For the Friday show, Blackman will share the stage with a group of tal…