docs: update output.assetModuleFilename type (#7145)

Author: snitin315

src/content/configuration/output.mdx

@@ -35,7 +35,7 @@ The top-level `output` key contains a set of options instructing webpack on how
 
 ## output.assetModuleFilename
 
-`string = '[hash][ext][query]'`
+`string = '[hash][ext][query]'` `function (pathData, assetInfo) => string`
 
 The same as [`output.filename`](#outputfilename) but for [Asset Modules](/guides/asset-modules/).