Twitter’s Periscope team has been secretly building an Apple TV app, TechCrunch reports. With Apple expected to unveil a new Apple TV set-top box tomorrow that includes an App Store (yet no official third-party SDK has been released), it seems Apple has approached some third-party developers quietly, in much the same way as the company handled its initial HomeKit rollout. Sources for the report confirm Periscope will be one of the first apps…