Feature request: support fixed filename

compilerOptions.output.chunkFilename is [name].[hash].js and i need to provide the generated name.hash.worker.js to sw-precache-webpack-plugin

I cant use the generated .worker.js filename, the [name] could not be used from /sw-precache-webpack-plugin (ok thats their problem) and the hash seems not to match the generated file.

An option to set a fixed target filename in webpack config would be perfect:

      new WorkerPlugin({
        filename: 'worker.js'
      }),

[developit]

I just implemented { filename, chunkFilename } options in #82.

[developit]

The filename option is now released in 5.0.0.