make serve missing bundle without first running build:webpack:docs

[seanupton]

make install && make serve result in 404 errors for http://localhost:8001/dist/mockup/bundle.min.js (on any supported node version I have tried).

There is not any output to _site/dist/mockup directory (which does not exist without webpack told to output to this target directory via npx yarn run build:webpack:docs).

If the interactive documentation is the primary vehicle for someone to develop and test basic changes to patterns (in a simpler vacuum outside of plone.staticresources), it might make sense to either:

1. Update Makefile(s) to include this by default as a dependency of make serve as some (new) bundle-docs target?
2. Update README.md development section to mention this is an explicit additional step needed to "run" the documentation?