finished implementation,ready for PR

resource/locales/ja_JP/translation.json

@@ -747,6 +747,6 @@
     "failed_to_create_admin_user":"管理ユーザーの作成に失敗しました。{{errMessage}}"
   },
   "grid_edit":{
-    "create_bootstrap_4_grid":"Create Bootstrap 4 Grid"
+    "create_bootstrap_4_grid":"Bootstrap 4 グリッドを作成"
   }
 }

resource/locales/zh_CN/translation.json

@@ -753,6 +753,6 @@
 		"failed_to_create_admin_user": "无法创建管理用户。{{errMessage}"
 	},
   "grid_edit":{
-    "create_bootstrap_4_grid":"Create Bootstrap 4 Grid"
+    "create_bootstrap_4_grid":"创建Bootstrap 4网格"
   }
 }

src/client/js/components/PageEditor/GridEditModal.jsx

@@ -276,10 +276,11 @@ class GridEditModal extends React.Component {
   }
 
   render() {
+    const { t } = this.props;
     return (
       <Modal isOpen={this.state.show} toggle={this.cancel} size="xl" className="grw-grid-edit-modal">
         <ModalHeader tag="h4" toggle={this.cancel} className="bg-primary text-light">
-          Create Bootstrap 4 Grid
+          {t('grid_edit.create_bootstrap_4_grid')}
         </ModalHeader>
         <ModalBody>
           <div className="container">
@@ -343,5 +344,6 @@ class GridEditModal extends React.Component {
 
 GridEditModal.propTypes = {
   onSave: PropTypes.func,
+  t: PropTypes.func.isRequired,
 };
 export default withTranslation('translation', { withRef: true })(GridEditModal);