There is no Receiptify library.
There are three jobs.
what you are assembling
Nobody publishes a package that builds a Receiptify-style Spotify receipt, because a receipt generator is not one problem. It is three, and they are wildly unequal. Job one: get the listening history out of Spotify, which means OAuth, one endpoint, and a quota policy that decides whether the app can ever have users. Job two: draw a page that looks like till paper. Job three: turn that page into a PNG the user can post.
Jobs two and three are a weekend and are solved several different ways, compared further down. Job one is the entire difficulty of the project, and almost every tutorial on this topic ends before reaching it. Anyone deciding what to build should read the quota section first, because it determines whether the other two are worth starting.
where Tearline sits
Tearline is jobs two and three in one custom element, and has nothing to do with job one. That is worth saying plainly at the top rather than at the bottom: it removes the easy work, not the hard work. If the Spotify side does not clear, no rendering library rescues the project.
receipt.html
Jobs two and three, complete. The markup stays real text in the light DOM, so the track titles are still selectable and still read in order by a screen reader, and the PNG is produced in the browser with no server. The rest of the API is in the reference.