Add a webext packaging target to the build script
Run npm run pack-webext -- 0.0.x
I imagine that'll do something like,
git clean -x -d -f webext/
require('webext/manifest.json').version = argv[1];
git commit -m "bump version to ${argv[1]}"
git tag argv[1]
git push --tags
npm run webext
zip webext
See comment:6:ticket:31087 for the original suggestion.