Allow use of booleans in the `externals` option
Allow use of booleans in the `externals` option

Fixes #3299

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