Recommend null instead of false for the first parameter of configureBabel()

Author: Lyrkan

index.js

@@ -787,7 +787,7 @@ class Encore {
      *      // change the babelConfig
      *      // if you use an external Babel configuration
      *      // this callback will NOT be used. In this case
-     *      // you can pass false as the first parameter to
+     *      // you can pass null as the first parameter to
      *      // still be able to use some of the options below
      *      // without a warning.
      * }, {
@@ -833,7 +833,7 @@ class Encore {
      *              file for instance). In this case you can set the option directly into
      *              that configuration file.
      *
-     * @param {function|false} callback
+     * @param {function|null} callback
      * @param {object} encoreOptions
      * @returns {Encore}
      */

test/WebpackConfig.js

@@ -621,14 +621,14 @@ describe('WebpackConfig object', () => {
         it('Calling with a whitelisted option when .babelrc is present works fine', () => {
             const config = createConfig();
             config.runtimeConfig.babelRcFileExists = true;
-            config.configureBabel(false, { includeNodeModules: ['foo'] });
+            config.configureBabel(null, { includeNodeModules: ['foo'] });
             expect(logger.getMessages().warning).to.be.empty;
         });
 
         it('Calling with a non-whitelisted option when .babelrc is present displays a warning', () => {
             const config = createConfig();
             config.runtimeConfig.babelRcFileExists = true;
-            config.configureBabel(false, { useBuiltIns: 'foo' });
+            config.configureBabel(null, { useBuiltIns: 'foo' });
 
             const warnings = logger.getMessages().warning;
             expect(warnings).to.have.lengthOf(1);