`wasm-pack fake` so CI tests and the like don't have to do any rust compilation

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💡 Feature description

add wasm-pack fake <package name> which generates a fake package to make TypeScript happy, and puts it right in node_modules.
So CI jobs don't have to spend like 5 minutes building rust just to type-check the TypeScript part of the project.

If you want to check against the WASM bindings you can just not use this feature.

I think the name of the module you want should be an argument so that, you don't even need to have the rust code (e.g., if it's in a submodule and you don't want to waste time downloading)

💻 Basic example

I think all that's necessary is to generate:

node_modules/foo/package.json

{
  "name": "foo",
  "types": "foo.d.ts"
}

node_modules/foo/foo.d.ts

declare module "foo";

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epic issue number