Add --no-html flag

[bwendt-mylo]

This issue is a:

• Bug report
• Feature request
• Question / support request
• Other

I'd like to run a build and have a single js file (no css necessary) generated in the output directory. I can get close by doing the following:

nwb build-preact-app --no-vendor

But I still always get the html and manifest.json files. Suggestions?

Would adding the following check in build-preact-app.js#buildConfig() do the trick?

  // ...
  plugins: {
    html: args.html !== false && getDefaultHTMLConfig(),
    vendor: args.vendor !== false
  },
  // ...

Thanks for taking a look!