refactor(es6): Upgrade ExternalsPlugin to es6 (#3621)
refactor(es6): Upgrade ExternalsPlugin to es6 (#3621)


EliteScientist/webpack,NekR/webpack,webpack/webpack,jescalan/webpack,cesarandreu/webpack,g0ddish/webpack,ts-webpack/webpack,g0ddish/webpack,SimenB/webpack,nkzawa/webpack,ts-webpack/webpack,SimenB/webpack,pugnascotia/webpack,rlugojr/webpack,ts-webpack/webpack,cesarandreu/webpack,rlugojr/webpack,rlugojr/webpack,EliteScientist/webpack,pugnascotia/webpack,nkzawa/webpack,cesarandreu/webpack,pugnascotia/webpack,webpack/webpack,webpack/webpack,SimenB/webpack,nkzawa/webpack,NekR/webpack,webpack/webpack,jescalan/webpack,ts-webpack/webpack,jescalan/webpack,SimenB/webpack,g0ddish/webpack