fix: set themes using new api

Author: wuweiweiwu

.storybook/main.js

@@ -1,4 +1,3 @@
-const path = require('path');
 module.exports = {
   stories: ['../stories/index.js'],
 };

.storybook/manager.js

@@ -0,0 +1,11 @@
+import { addons } from '@storybook/addons';
+import { create } from '@storybook/theming/create';
+
+addons.setConfig({
+  theme: create({
+    base: 'light',
+    brandTitle: 'React Sortable Tree',
+    brandUrl: 'https://github.com/frontend-collective/react-sortable-tree',
+    gridCellSize: 12,
+  }),
+});

package.json

@@ -88,6 +88,7 @@
     "@storybook/addon-storyshots": "^5.2.6",
     "@storybook/addons": "^5.3.17",
     "@storybook/react": "^5.2.6",
+    "@storybook/theming": "^5.3.17",
     "autoprefixer": "^9.7.1",
     "babel-core": "^7.0.0-bridge.0",
     "babel-eslint": "^10.0.3",

yarn.lock

@@ -1859,7 +1859,7 @@
     qs "^6.6.0"
     util-deprecate "^1.0.2"
 
-"@storybook/theming@5.3.17":
+"@storybook/theming@5.3.17", "@storybook/theming@^5.3.17":
   version "5.3.17"
   resolved "https://registry.yarnpkg.com/@storybook/theming/-/theming-5.3.17.tgz#cf6278c4857229c7167faf04d5b2206bc5ee04e1"
   integrity sha512-4JeOZnDDHtb4LOt5sXe/s1Jhbb2UPsr8zL9NWmKJmTsgnyTvBipNHOmFYDUsIacB5K4GXSqm+cZ7Z4AkUgWCDw==