Webpack's module concatenation support was broken by v15 due to this `module.exports` line. Changing to ESM export fixes this issue.

ref #1219

BREAKING CHANGE: <template lang="xxx"> are now handled
with webpack loaders as well.

fix #1213

fix #1214

close #1199

* fix(loader): use options.minimize

* misc(loader): rename options.minimize ~> options. productionMode

* feat(doc): add productionMode to options list