Integrate WASM with Scala CLI

[Gedochao]

Is your feature request related to a problem? Please describe. We currently support emitting Wasm via Scala.js, but we do not yet integrate it with Scala CLI features.

Describe the solution you'd like I'd like to be able to run Scala code with Wasm directly from Scala CLI. Additionally, I'd like to be able to choose a runtime and let Scala CLI download it for me. Unsure which runtimes should be supported, + we should likely have a default.

• [ ] support running Wasm from Scala CLI
  • [ ] a CLI flag --wasm
  • [ ] a corresponding directive, likely a wasm param for the platform directive
• [ ] allow to pick a Wasm runtime + have a default
  • [ ] command line option
  • [ ] directive
• [ ] consider Wasm for other Scala CLI features (likely out of scope) and create follow-up issues

Additional context

• initial support for WASM: #3213

cc @sjrd @tanishiking

[sjrd]

Note that currently, the Wasm support of Scala.js always emits JS+Wasm files. So you need a JS runtime to run it, like the existing Scala.js-on-JS.

In addition, one may need to provide specific flags to the engine, in order to enable experimental Wasm features that Scala.js-on-Wasm needs. See https://www.scala-js.org/doc/project/webassembly.html