docs(configuration): describe layer option (#6274)

* describe layer option

* Update src/content/configuration/module.mdx

Co-authored-by: Sam Chen <[email protected]>

Author: vankop

src/content/configuration/module.mdx

@@ -528,7 +528,7 @@ module.exports = {
 
 `string`
 
-Specify the layer in which the module should be placed in.
+Specify the layer in which the module should be placed in. A group of modules could be united in one layer which could then be used in [split chunks](/plugins/split-chunks-plugin/#splitchunkslayer), [stats](/configuration/stats/#statsgroupmodulesbylayer) or [entry options](/configuration/entry-context/#entry-descriptor).
 
 **webpack.config.js**