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-document.md

@@ -0,0 +1,55 @@
+---
+sidebar_position: 2
+---
+
+# Create a Document
+
+Documents are **groups of pages** connected through:
+
+- a **sidebar**
+- **previous/next navigation**
+- **versioning**
+
+## Create your first Doc
+
+Create a markdown file at `docs/hello.md`:
+
+```md title="docs/hello.md"
+# Hello
+
+This is my **first Docusaurus document**!
+```
+
+A new document is now available at `http://localhost:3000/docs/hello`.
+
+## Configure the Sidebar
+
+Docusaurus automatically **creates a sidebar** from the `docs` folder.
+
+Add metadatas to customize the sidebar label and position:
+
+```md title="docs/hello.md" {1-4}
+---
+sidebar_label: 'Hi!'
+sidebar_position: 3
+---
+
+# Hello
+
+This is my **first Docusaurus document**!
+```
+
+It is also possible to create your sidebar explicitly in `sidebars.js`:
+
+```diff title="sidebars.js"
+module.exports = {
+  tutorialSidebar: [
+    {
+      type: 'category',
+      label: 'Tutorial',
+-     items: [...],
++     items: ['hello'],
+    },
+  ],
+};
+```