Firefox Desktop, Firefox Android, and Firefox iOS all already initialize viaduct. You only need to
take action if you want to use the Rust components on a new application.
There are 3 different options to use `viaduct`:
* Any `libxul` based can ignore initialization, since it's handled by `libxul`.
* Using the reqwest backend, which uses the `reqwest` library and a `reqwest`-managed thread.
* Implementing the C FFI like `libxul` does (https://searchfox.org/mozilla-central/source/toolkit/components/viaduct).
