Use npx babel-upgrade --write --install to initiate the upgrade. Then update grunt and rollup.
Decreases minified, gzipped filesize by about 1KB. Decreases build times by a few minutes.
This is upgrades rollup and uglify to latest versions. It also rewrites the rollup config to take advantage of the newest features of rollup. Minification is also split up into a separate process, mostly to speed up the build. The total build type can go down from about 2.5 minutes to around 1 minute for all the generated javascript files.
