Allows us to get rid of build.rs, which was only used to
compile resources. static_resource.rs is now created by
meson, and the meson path is used for include_bytes!.
Previously we were using the env! macro to determine
build-time variables like version, app ID, and locale dir.
Instead of relying on env vars, we can create a configuration
file with meson and import it.
I've simplified the project, removing all the tokio communication stuff
and the ruma-client, calling directly to the Matrix.org API using the
reqwest rust lib.
