Lodash: Refactor away from _.mergeWith() (WordPress#51483)

* Lodash: Refactor away from _.mergeWith()

* Add back the comment

* Update package-lock.json

.eslintrc.js

@@ -110,6 +110,7 @@ const restrictedImports = [
 			'maxBy',
 			'memoize',
 			'merge',
+			'mergeWith',
 			'negate',
 			'noop',
 			'nth',

packages/edit-site/package.json

@@ -66,8 +66,10 @@
 		"@wordpress/wordcount": "file:../wordcount",
 		"classnames": "^2.3.1",
 		"colord": "^2.9.2",
+		"deepmerge": "^4.3.0",
 		"downloadjs": "^1.4.7",
 		"fast-deep-equal": "^3.1.3",
+		"is-plain-object": "^5.0.0",
 		"lodash": "^4.17.21",
 		"memize": "^2.1.0",
 		"react-autosize-textarea": "^7.1.0",

packages/edit-site/src/components/global-styles/global-styles-provider.js

@@ -1,7 +1,8 @@
 /**
  * External dependencies
  */
-import { mergeWith } from 'lodash';
+import deepmerge from 'deepmerge';
+import { isPlainObject } from 'is-plain-object';
 
 /**
  * WordPress dependencies
@@ -21,17 +22,13 @@ const { GlobalStylesContext, cleanEmptyObject } = unlock(
 	blockEditorPrivateApis
 );
 
-function mergeTreesCustomizer( _, srcValue ) {
-	// We only pass as arrays the presets,
-	// in which case we want the new array of values
-	// to override the old array (no merging).
-	if ( Array.isArray( srcValue ) ) {
-		return srcValue;
-	}
-}
-
 export function mergeBaseAndUserConfigs( base, user ) {
-	return mergeWith( {}, base, user, mergeTreesCustomizer );
+	return deepmerge( base, user, {
+		// We only pass as arrays the presets,
+		// in which case we want the new array of values
+		// to override the old array (no merging).
+		isMergeableObject: isPlainObject,
+	} );
 }
 
 function useGlobalStylesUserConfig() {