The makers of ChatGPT are broadening the horizon of their AI-powered software with a new feature that allows users to create up to a minute of video footage from text prompts. The AI model, named Sora, is first being made available to a limited number of creative professionals, OpenAI chief executive Sam Altman announced on the social media platform X on Thursday. OpenAI published several demo videos, all generated entirely by artificial intelligence, on the software’s website, along with the description on which they were based. One of them shows a woman walking through a brightly lit city st…