refactor(cli): improve typing of window

In order to be able to extend types in global scope with an `import` at the top of the file we have to create a new dedicated file (and can not use already existing typings.d.ts).
For details, see https://stackoverflow.com/questions/30960386/how-to-extend-the-window-typescript-interface/30961346#30961346

lib/cli/src/extract.ts

@@ -17,7 +17,7 @@ const read = async (url: string) => {
   const data = JSON.parse(
     await page.evaluate(async () => {
       // eslint-disable-next-line no-undef
-      const d = (window as any).__STORYBOOK_STORY_STORE__.extract();
+      const d = window.__STORYBOOK_STORY_STORE__.extract();
 
       const result = Object.entries(d).reduce(
         (acc, [k, v]: [string, any]) => ({

lib/cli/src/window.d.ts

@@ -0,0 +1,7 @@
+import { StoryStore } from '@storybook/client-api';
+
+declare global {
+  interface Window {
+    __STORYBOOK_STORY_STORE__: StoryStore;
+  }
+}