docs(configuration): add optimization.realContentHash (#3919)

Author: jamesgeorge007

src/content/configuration/optimization.md

@@ -571,3 +571,20 @@ module.exports = {
   }
 };
 ```
+
+## `optimization.realContentHash`
+
+`boolean = true`
+
+Adds an additional hash compilation pass after the assets have been processed to get the correct asset content hashes. If `realContentHash` is set to `false`, internal data is used to calculate the hash and it can change when assets are identical.
+
+__webpack.config.js__
+
+```js
+module.exports = {
+  //...
+  optimization: {
+    realContentHash: false
+  }
+};
+```