[lib] expose opaque-ke library to Node

Summary:
Neon provides bindings for writing Node.js addons in Rust. We will call the opaque-ke registration/login functions through this addon.

Adding @ashoat because of the new dependency. More context here: https://linear.app/comm/issue/ENG-2289/use-opaque-ke-to-handle-pake-registrationlogin-on-keyserver-side

Test Plan: run cargo build in the opaque-ke-cxx directory, the library compiles

Reviewers: ashoat, atul, tomek, bartek

Reviewed By: ashoat, tomek, bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D5685