Missing support for trunk, which is used to build Rust WebAssembly frontends

[xfbs]

Trunk is a tool used to build, bundle and ship Rust WebAssembly frontends. Since WebAssembly frontends need a little bit of glue code to talk to browser APIs, a tool such as Trunk is necessary to turn a WASM binary into something a browser and load and execute.

I believe that we should add support for trunk to kraken, such that it can build WebAssembly frontends without needing too much manual configuration. If possible, we might even be able to enable autoconf to detect it by the presence of a Trunk.toml file.