Adds a note about the typedefs for typescript support

[orta]

This is mainly to re-direct people to see a bunch of example code if they're using the typedefs, as https://github.com/DefinitelyTyped/DefinitelyTyped/pull/27221 is both elegant but a bit tricky to do yourself without a reference.

[alloy]

Thanks @orta 👌

[tizmagik]

Thanks @orta ! Swing by the office next time you're around 😁