Alongside Maya Hawke, Andrew Garfield does his best Joker impression in Gia Coppola’s Black Mirror-esque critique of social media. — It’s a cliché nowadays to say that we’re all slaves to our phones and social media, but it’s an analogy worth keeping in mind when thinking about Mainstream. Even more so, the words of self-described “Black, lesbian, mother, warrior, poet” Audre Lorde, who wrote that “the master’s tools will never…