Use only core in browser environment, loader in node env

packages/kbn-i18n/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@kbn/i18n",
-  "browser": "./target/web",
-  "main": "./target/node",
+  "browser": "./target/web/browser.js",
+  "main": "./target/node/index.js",
   "module": "./src/index.js",
   "version": "1.0.0",
   "license": "Apache-2.0",

packages/kbn-i18n/src/browser.js

@@ -0,0 +1,22 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import * as i18nCore from './core';
+
+export const i18n = i18nCore;

packages/kbn-i18n/src/index.js

@@ -17,8 +17,8 @@
  * under the License.
  */
 
-import * as i18nCore from './core';
 import * as loader from './loader';
+import * as i18nCore from './core';
 
 export const i18n = i18nCore;
 export const i18nLoader = loader;