Update js-dce example for Kotlin 1.3.50

[nanodeath]

Kotlin 1.3.40 saw the release of a new KotlinJS plugin, org.jetbrains.kotlin.js. apply plugin: 'kotlin-dce-js' still seems to work, but the buildBundle part doesn't, as NpmTask doesn't exist anymore.

Can we update the example? Otherwise it's tricky to see how to properly use DCE, since it spits out a bunch of separate files.

[er453r]

Sorry guys, but HOW to use the DCE in js project from 1.3.40 and up (using kotlin.js)? I ca't figure this out...