Adds Asciidoctor.js + Opal Node runtime/compiler

[ggrossetie]

Asciidoctor.js is using Opal to compile Asciidoctor Ruby in JavaScript.

Opal Node runtime is a Node module of Opal "base" modules:

• base64.js
• nodejs.js
• opal.js
• pathname.js

Opal Node compiler is a Node module of Opal builder module. It can be useful if you want to compile a Ruby library in a JavaScript build (ie. without installing Ruby).

[fazibear]

THanks for your contibutions!

[ggrossetie]

Thanks to you 😄