Jco transpile: implementation of wasi-nn for Web

[danbev]

This issue is intended for tracking adding a shim for wasi-nn.

Tasks:

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[danbev]

Hope it is alright that I created this issue without any actual tasks. I'm not sure what needs to be done or how these shims are created but hopefully others might be able to add some tasks for this.

[guybedford]

This would be great to see! The goal for Jco is to support all WASI staged proposals automatically so they can work out of the box. Some details on how the integration can be designed via automatic map configuration is provided in https://bytecodealliance.github.io/jco/transpiling.html#wasi-proposals. By posting this issue you have now volunteered you realise :P