[Tracker] Switch to a better build system

[debloper]

It may be worth trying out alternative build systems to weigh webpack's pros/cons. RollupJS looks very promising in that regard. It's more focused, lean, efficient and generates smaller bundles (at least on paper). Here's a reference/example implementation: facebook/react#9327

Also, parcel-bundler is another alternative zero-config build+bundling tool, may be worth looking into.

Tasks

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Ref dump for webpack version update/migration:

• https://webpack.js.org/guides/migrating/
• https://medium.com/webpack/webpack-3-official-release-15fd2dd8f07b