* chore: migrate src/Page.js to TypeScript
The final one! This is a huge file and needs to be split up and tidied,
but for now I've left all the definitions in place and converted types
accordingly.
There's some additional tidying we can do now every `src` file is TS,
but I'll leave that for another PR to avoid this one getting any bigger.
Co-authored-by: Mathias Bynens <mathias@qiwi.be>
