Make MerJS deployable on Fastly Compute (Compute@Edge)

[jedisct1]

Problem / motivation

MerJS applications can be deployed to Cloudflare, but not to Fastly.

Fastly has native support for WebAssembly execution, and it's quite easy to make MerJS applications work on it.

Proposed solution

Compile a MerJS app to wasm32-wasi and run it directly on Fastly Compute without a JS shim.

Static assets have to be embedded in the wasm binary, but this is easy to do at compile-time.

Alternatives considered

Additional context