SonderCo, the Santa Monica, CA-based marketing and talent agency that brokers brand partnerships with celebrities, creators, influencers and others, has promoted Jessie Mash to president, a new role at the agency.   Mash was previously head of talent partnerships and is credited with developing deals that paired Teyana Taylor and Doja Cat with Ray-Ban Meta, Rebel Wilson with Noom, and Salma Hayek with Ultherapy, along with campaigns featuring Shaun White, Millie Bobby Brown, Martha Stewart …