[Deps] Handle decorators properly with acorn so that vue-gettext fetches translations properly
Our front translation system uses Vue-Gettext that uses easygettext to extract strings from code. To do that it uses acorn to parse JS, but acorn doesn't support decorators (which aren't ECMA-script stage 3 yet).
See https://github.com/Polyconseil/easygettext/issues/49 and https://github.com/tcitworld/acorn-es7