docs(config): add functions as valid output.filename type (#1751)

This change corresponds to the following PR:

webpack/webpack#6144

Author: Jake Todaro

src/content/configuration/output.md

@@ -64,7 +64,7 @@ auxiliaryComment: {
 
 ## `output.chunkFilename`
 
-`string`
+`string` `function`
 
 This option determines the name of non-entry chunk files. See [`output.filename`](#output-filename) option for details on the possible values.
 
@@ -166,7 +166,7 @@ If multiple modules would result in the same name, [`output.devtoolFallbackModul
 
 ## `output.filename`
 
-`string`
+`string` `function`
 
 This option determines the name of each output bundle. The bundle is written to the directory specified by the [`output.path`](#output-path) option.
 
@@ -206,7 +206,7 @@ Make sure to read the [Caching guide](/guides/caching) for details. There are mo
 
 Note this option is called filename but you are still allowed to use something like `"js/[name]/bundle.js"` to create a folder structure.
 
-Note this options does not affect output files for on-demand-loaded chunks. For these files the [`output.chunkFilename`](#output-chunkfilename) option is used. It also doesn't affect files created by loaders. For these files see loader options.
+Note this option does not affect output files for on-demand-loaded chunks. For these files the [`output.chunkFilename`](#output-chunkfilename) option is used. Files created by loaders also aren't affected. In this case you would have to try the specific loader's available options.
 
 The following substitutions are available in template strings (via webpack's internal [`TemplatedPathPlugin`](https://github.com/webpack/webpack/blob/master/lib/TemplatedPathPlugin.js)):
 
@@ -220,6 +220,8 @@ The following substitutions are available in template strings (via webpack's int
 
 The lengths of `[hash]` and `[chunkhash]` can be specified using `[hash:16]` (defaults to 20). Alternatively, specify [`output.hashDigestLength`](#output-hashdigestlength) to configure the length globally.
 
+If using a function for this option, the function will be passed an object containing the substitutions in the table above.
+
 T> When using the [`ExtractTextWebpackPlugin`](/plugins/extract-text-webpack-plugin), use `[contenthash]` to obtain a hash of the extracted file (neither `[hash]` nor `[chunkhash]` work).
 
 
@@ -245,7 +247,7 @@ An optional salt to update the hash via Node.JS' [`hash.update`](https://nodejs.
 
 ## `output.hotUpdateChunkFilename`
 
-`string`
+`string` `function`
 
 Customize the filenames of hot update chunks. See [`output.filename`](#output-filename) option for details on the possible values.
 
@@ -271,7 +273,7 @@ For details see [`output.jsonpFunction`](#output-jsonpfunction).
 
 ## `output.hotUpdateMainFilename`
 
-`string`
+`string` `function`
 
 Customize the main hot update filename. See [`output.filename`](#output-filename) option for details on the possible values.
 
@@ -607,7 +609,7 @@ Note it also adds some info about tree shaking to the generated bundle.
 
 ## `output.publicPath`
 
-`string`
+`string` `function`
 
 This is an important option when using on-demand-loading or loading external resources like images, files, etc. If an incorrect value is specified you'll receive 404 errors while loading these resources.