ThemeContext

Let's quickly do ThemeContext.tsx

// replace
const ThemeContext = createContext<[string, (theme: string) => void]>([
  "green",
  () => {},
]);

• Here we just have to tell TS that we have a strict ordering of string and function. This will make other files easier to type.
• We're telling it that this function will accept a string which TypeScript will enforce for us later.