Don't include documentation in NPM package
Don't include documentation in NPM package

I accidentally forgot to exclude the built documentation in #3243.

To test this run `npm run release` followed by `npm pack`.  This will
produce `cesium-1.16.0.tgz`, which you can unpack and inspect to make
sure Build/Documentation does not exist.

NaderCHASER/cesium,NaderCHASER/cesium,denverpierce/cesium,soceur/cesium,hodbauer/cesium,AnalyticalGraphicsInc/cesium,denverpierce/cesium,jasonbeverage/cesium,aelatgt/cesium,emackey/cesium,esraerik/cesium,jason-crow/cesium,progsung/cesium,josh-bernstein/cesium,jason-crow/cesium,omh1280/cesium,ggetz/cesium,wallw-bits/cesium,wallw-bits/cesium,kaktus40/cesium,geoscan/cesium,likangning93/cesium,denverpierce/cesium,ggetz/cesium,kiselev-dv/cesium,omh1280/cesium,CesiumGS/cesium,emackey/cesium,oterral/cesium,kiselev-dv/cesium,hodbauer/cesium,NaderCHASER/cesium,esraerik/cesium,denverpierce/cesium,emackey/cesium,AnimatedRNG/cesium,kiselev-dv/cesium,YonatanKra/cesium,wallw-bits/cesium,AnimatedRNG/cesium,soceur/cesium,ggetz/cesium,hodbauer/cesium,ggetz/cesium,wallw-bits/cesium,jasonbeverage/cesium,emackey/cesium,YonatanKra/cesium,jason-crow/cesium,progsung/cesium,CesiumGS/cesium,oterral/cesium,aelatgt/cesium,geoscan/cesium,kiselev-dv/cesium,CesiumGS/cesium,likangning93/cesium,aelatgt/cesium,esraerik/cesium,soceur/cesium,CesiumGS/cesium,esraerik/cesium,omh1280/cesium,oterral/cesium,aelatgt/cesium,jason-crow/cesium,omh1280/cesium,AnimatedRNG/cesium,likangning93/cesium,kaktus40/cesium,josh-bernstein/cesium,AnimatedRNG/cesium,CesiumGS/cesium,YonatanKra/cesium,AnalyticalGraphicsInc/cesium,YonatanKra/cesium,likangning93/cesium,likangning93/cesium