The Web AppBuilder Widget Generator has hit v3, which brings with it the ability to generate widgets in TypeScript, and the functionality to create a "build" of your apps that you've created. Also, you can enable LiveReload to have your browser automatically refresh when you make a file change, saving you tons of time during development. Full details: Release v3.0.0 · Esri/generator-esri-appbuilder-js · GitHub
Questions or comments? Feel free to comment here. Issues? Please create an issue in GitHub.
Bonus: George Bochenek and I presented about this and other advanced development topics last week at Dev Summit 2018. The video will be released within a few weeks, but for now you can find the slides and follow the repo to get updates when the video comes out: GitHub - gavinr/web-appbuilder-tools-techniques-dev-summit-2018