The only good binary clock app I can find on Android is so old that you can't access its limited customization menu without a hardware menu button. As such, I want to make my own, and I see this as a good excuse to practice the basics of React Native in a simple app. This commit is basically just the result of `react-native init` with the TypeScript template, but I did figure out how to show the clock as a sequence of periods that updates over time. I have other homework to focus on now, but this has been a satisfying start.