Adding an external extension

If an Asciidoctor.js extension is not already supported in this plugin suite, there is a there is a special extension of type AsciidoctorjsGenericExtension.

Groovy

import org.asciidoctor.gradle.model5.js.extensions.AsciidoctorjsGenericExtension

asciidoc {
  toolchains {
    asciidoctorjs.asciidocExtensions {
      myBackend(AsciidoctorjsGenericExtension) {
        attributes( foo_color : 'black') (1)
        requires 'foo' (2)
        usePackage( 'asciidoctor', 'foo', '1.2.3') (3)
        usePackage( 'asciidoctor-emoji', '1.2.3') (4)
      }
    }
  }
}

1	Set the specific attributes that this extension might require.
2	If one or more `requires` need to be passed to the engine, define them here.
3	Add the NPM package details. The first parameter is the scope and can be passed as `null`. The second parameter is the package name. The third parameter is something that can be lazy-evaluated to a version string.
4	A two-parameter version if the package is scope-less.