Yarn package manager install offline support

[jmeberst]

I'm using the yarn package manager (v0.27.5) to install my modules including plotly offline behind a corporate proxy. [email protected] has a dependency on two packages (mapbox-gl-shaders, and mapbox-gl-specs) that have been removed on github, and yarn won't correctly package them into the tgz files it uses for the offline registry.

[etpinard]

Nothing we can do until #1714 is ✅

Closing.