How do you get your first contributors to a new open-source project?

I released a mid-size TypeScript project (a social publishing API) under Apache 2.0 a couple of weeks ago. The repo is clean, there are good-first-issue labels, the documentation is good. Stars are trickling in. (Very, very slowly) I got a few contributors to my repo out of nowhere, and I loved that. Merged their PRs, and they never followed up after. Which is fair. It's new and nobody owes me their weekend. For those of you who've taken a project from "just me" to a real contributor base, what ended up wor