Add support for library projects

[Toilal]

Library project with 2 outputs : library and demo.

[dvic]

Do you think this should go in the same template? (asking a question whether the user wants a library or an app?)

[Toilal]

Yes, I think it should be in the same template, but during generation we need to generate most files in ./demo/ instead of ./src/, and it's not possible with actual vue-cli version.

I have a Pull Request on vue-cli to support extending metalsmith (the generator used under the hoods for vue-init).

Alternative that will work with actual vue-cli release is to duplicate ./src files into ./demo and use vue-cli filters, until this pull request is merged and released.

[Toilal]

A library should also be published as a single file CommonJS ES5 bundle in package.json main property, and as ES2015 modules in module property.

[Toilal]

vue-cli has been released with my Pull Request merged, so i'll be able to work on this now.

[Toilal]

It's here ! @dvic if you are still here, maybe you can give it a try ?

[dvic]

Hi! Looks good, thanks! I'm really looking forward to Vue 2.5: https://medium.com/the-vue-point/upcoming-typescript-changes-in-vue-2-5-e9bd7e2ecf08 (see vuejs/vue#6391).

[Toilal]

Yes, I read this article too. When it's out, i'll upgrade this boilerplate.

[Toilal]

@dvic => 2.5 is out : https://github.com/vuejs/vue/releases