Correct emitFile content argument type
Correct emitFile content argument type

As stated in the documentation, and proven in practice, `emitFile` accepts a buffer for the content argument. Currently, passing one results in a type error. This corrects the argument type.
webpack/webpack,SimenB/webpack,webpack/webpack,webpack/webpack,webpack/webpack,SimenB/webpack,SimenB/webpack,SimenB/webpack