Use terser-webpack-plugin instead of uglifyjs-webpack-plugin

[banyan]

webpack and create-react-app switched from uglifyjs-webpack-plugin to terser-webpack-plugin. The reason is well written at webpack/webpack#8036 (comment). what do you think about to switch?

refs: https://twitter.com/dan_abramov/status/1060122100340588545

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we don't need a workaround as create-react-app does at https://github.com/facebook/create-react-app/blob/5352a0c/packages/react-scripts/config/webpack.config.js#L204-L208 since it's fixed and we use terser version 3.10.12 in this PR.

[jakeNiemiec]

For some popular, asset heavy libraries, uglifyjs-webpack-plugin produces show-stopping issues (e.g.: Font Awesome):
https://fontawesome.com/how-to-use/with-the-api/other/tree-shaking#issues
FortAwesome/Font-Awesome#13260

Thanks for this PR.

[gauravtiwari]

thanks :)