chore: add comments

packages/webpack-cli/lib/utils/warnings/bailAndWatchWarning.js

@@ -1,7 +1,14 @@
 const logger = require('../logger');
 
-module.exports = (compiler) => {
+/**
+ * warn the user if bail and watch both are used together
+ * @param {Object} webpack compiler
+ * @returns {void}
+ */
+const bailAndWatchWarning = (compiler) => {
     if (compiler.options.bail && compiler.options.watch) {
         logger.warn('You are using "bail" with "watch". "bail" will still exit webpack when the first error is found.');
     }
 };
+
+module.exports = bailAndWatchWarning;