Some kind of file watcher for wasm and dictionary files?

[avidal]

One option is using an in-process file watcher, which would reload file-based dictionaries specified in the CLI and/or the wasm file passed in. Another option would be a SIGHUP handler which can reload the same.

I'm leaning towards a SIGHUP handler, then callers can use whatever mechanism they want to do the reload itself, such as watchexec.

In either case, the library itself would need to expose a mechanism to gracefully reload. Since Fastlike is actually implemented as a pool, reloading should be simple enough: stop accepting requests, empty the pool, and replace it with a new instanceFn.