fix(lib/WebpackError): make use of nodejs.util.inspect.custom

lib/WebpackError.js

@@ -4,6 +4,8 @@
 */
 "use strict";
 
+const inspect = require("util").inspect.custom;
+
 class WebpackError extends Error {
 	/**
 	 * Creates an instance of WebpackError.
@@ -21,7 +23,7 @@ class WebpackError extends Error {
 		Error.captureStackTrace(this, this.constructor);
 	}
 
-	inspect() {
+	[inspect]() {
 		return this.stack + (this.details ? `\n${this.details}` : "");
 	}
 }