L.A.’s beloved food writer on his origin story, the myth of authenticity, the art of constructive criticism, the futility of Yelp, and what makes our city so great — You only have to care about one of three things to be a fan of Jonathan Gold’s work: good food, great writing, or the city of Los Angeles. And if you love all three, like I do, you are devastated by his death this week. In 2016, I got an…