feat: npm init docusaurus, yarn create docusaurus (#5635)

* initial create-docusaurus impl

* cleanup

* @docusaurus/init renamed to create-docusaurus

* 0.0.6

* update lockfile

* fix lint

* remove npm2yarn for "npm init" because npm2yarn doesn't convert it and yarn result fails to execute

* prettier

* add correct version

* prettier

* prettier

* prettier

* prettier

* fix annoying --config .prettierrc issue

packages/create-docusaurus/templates/shared/docs/tutorial-basics/create-a-page.md

@@ -0,0 +1,43 @@
+---
+sidebar_position: 1
+---
+
+# Create a Page
+
+Add **Markdown or React** files to `src/pages` to create a **standalone page**:
+
+- `src/pages/index.js` -> `localhost:3000/`
+- `src/pages/foo.md` -> `localhost:3000/foo`
+- `src/pages/foo/bar.js` -> `localhost:3000/foo/bar`
+
+## Create your first React Page
+
+Create a file at `src/pages/my-react-page.js`:
+
+```jsx title="src/pages/my-react-page.js"
+import React from 'react';
+import Layout from '@theme/Layout';
+
+export default function MyReactPage() {
+  return (
+    <Layout>
+      <h1>My React page</h1>
+      <p>This is a React page</p>
+    </Layout>
+  );
+}
+```
+
+A new page is now available at `http://localhost:3000/my-react-page`.
+
+## Create your first Markdown Page
+
+Create a file at `src/pages/my-markdown-page.md`:
+
+```mdx title="src/pages/my-markdown-page.md"
+# My Markdown page
+
+This is a Markdown page
+```
+
+A new page is now available at `http://localhost:3000/my-markdown-page`.