Package django-webpack-loader 1.0 for debian

django-webpack-loader recently pushed its 1.0 release and it introduces breaking changes since previous versions.

django-webpack-loader 1.0 is not packaged in debian and few chances that it will be distributed in buster so we will have to package it ourselves.

The package is quite lightweight so this should not be too complicated to do.

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Migrated from T3330 (view on Phabricator)