Publish compiler as npm package

[bhelx]

It might make sense to publish the whole package to npm and have the compiler published as a bin since that's how most people will be managing their other dependencies. We can also add it to the templates. There may be some trickiness around getting wasm-merge in place. Leaving this open for discussion and ideas on how to implement.

[Phault]

Seems fairly feasible to package it up. While I think it would be unwise to use this dependency due to its outdated dependencies, it can serve as a great reference either way: binary-install example. Someone also went through the trouble of rewriting it without axios: simple-binary-install.

Apparently binaryen npm package already contains wasm-merge and wasm-opt bins, and I can confirm extism-js works just fine with them. So this is just a matter of adding it as a peerDep.

Edit: Once again I've been duped by npm's hoisting behavior. Seems there's a bit more to it, on top of adding it as peerDep, as binaries of transient deps aren't hoisted.

So wasm-merge won't automatically become available for the plugin developer to directly call, unless they add it as a dep themselves. I believe it would be available to the extism-js binary that we'll bundle though, so it should be a non-issue.

[ubiquitous-dev]

This would be really awesome to see, it would make the process of using the pdk super streamlined for node devs. Also, it unlocks npx flows where you could execute a build without even having to install it locally, which is really great for quick-starting.