For film fans, you may think of Jac Shaeffer and remember her 2009 debut film, “Timer,” which made the rounds at film festivals. However, in more recent years, she’s been a prominent screenwriter, especially at Marvel Studios, where she contributed to films such as “Captain Marvel” and the forthcoming “Black Widow.” But her most recent project is the Disney+ series, “WandaVision,” which she created and produces. It’s “WandaVision” that might end up being one of the most important Marvel Studios creations yet, serving as the company’s debut into the world of TV and streaming. And Jac Shaeffer couldn’t be more excited to lead the way.