From watching HN, it seems one valid approach is to start your repo on GitHub (or GitLab -- seems to be more trendy this week), write up a good readme.md page and maybe a functional pre-alpha set of code, then post it to HN as a "Show HN" or "Announcing WASM Parrot: the Perl to WebAssembly compiler" or whatever the title/purpose of the project is.

Lather, rinse, repeat on Reddit.

Actually, the "how to announce a project" would make for a great topic in an expanded FAQ.