add globalObject to webpack prod build for ability to build in node

[jantznick]

I was trying to use chessboardjsx in a project with server side rendering. Since some of it accesses the window object it was breaking my webpack server build since there is no window object on the server.

I came across this info that shows how to resolve this: https://webpack.js.org/configuration/output/#outputglobalobject

When testing on my local build this seems to resolve the issue.

[ottomated]

+1