Set up GitHub Action that will do a fresh compile of the rust "app-server" crate on each commit, and record the "--timings" html output into "debate-map/compile-timings" repo

[Venryx]

How to have Rust record compile-timings info: https://doc.rust-lang.org/cargo/reference/timings.html

GitHub actions docs (entry point): https://docs.github.com/en/actions