Move Storybook to the root

Signed-off-by: Charles de Dreuille <charles.dedreuille@gmail.com>

.storybook/main.ts

@@ -0,0 +1,49 @@
+import type { StorybookConfig } from '@storybook/react-vite';
+
+import { join, dirname, posix } from 'path';
+
+// This set of stories are the ones that we publish to backstage.io.
+const backstageCoreStories = [
+  'packages/ui',
+  'packages/core-components',
+  'packages/app',
+  'plugins/org',
+  'plugins/search',
+  'plugins/search-react',
+  'plugins/home',
+  'plugins/catalog-react',
+];
+
+const rootPath = '../';
+const storiesSrcMdx = 'src/**/*.mdx';
+const storiesSrcGlob = 'src/**/*.stories.@(js|jsx|mjs|ts|tsx)';
+
+const getStoriesPath = (element: string, pattern: string) =>
+  posix.join(rootPath, element, pattern);
+
+const stories = backstageCoreStories.flatMap(element => [
+  getStoriesPath(element, storiesSrcMdx),
+  getStoriesPath(element, storiesSrcGlob),
+]);
+
+// Resolve absolute path of a package. Needed in monorepos.
+function getAbsolutePath(value: string): any {
+  return dirname(require.resolve(join(value, 'package.json')));
+}
+
+const config: StorybookConfig = {
+  stories,
+  addons: [
+    getAbsolutePath('@storybook/addon-links'),
+    getAbsolutePath('@storybook/addon-essentials'),
+    getAbsolutePath('@storybook/addon-interactions'),
+    getAbsolutePath('@storybook/addon-themes'),
+    getAbsolutePath('@storybook/addon-storysource'),
+  ],
+  framework: {
+    name: getAbsolutePath('@storybook/react-vite'),
+    options: {},
+  },
+};
+
+export default config;