Emma McIntyre/Getty Images for Prime Video MrBeast teased a new membership program at a private advertiser meeting. The world's biggest YouTuber also touted plans to expand into content areas such as food and finance. The gathering during TV upfronts week was a sign of how big creators are gunning for TV ad dollars. MrBeast is planning a membership program as the world's biggest social media star looks beyond YouTube to build a diversified entertainment company. Beast Industries executives shared the news Tuesday at an invite-only breakfast for brand and ad executives and industry insiders at Penthouse 45, a swanky Manhattan event venue. On tap were Jimmy Donaldson (aka MrBeast), Beast Industries CEO Jeffrey Housenbold, and Partnerships SVP Beau Avril. Coinciding with the annual TV upfronts week , when legacy TV companies like NBCUniversal and Disney make their big pitches to advertisers, it showed how top creators are now competing with entertainment giants for brand budgets.…