Create an npm package for flexlint

[seveibar]

I like this repo conceptually and would like to use it in tscircuit's many repos to forbid specific things, like the use of "data" as a variable.

I think flexlint should be available as an npm package, this can be done by downloading the binary in a postinstall step, or compiling to WASM with a small JS wrapper around the wasm.

Ideally I can specify flexlint as a package.json lint step like so:

{
  "scripts": {
    "lint": "flexlint"
  }
}

...and have it read the config and lint.