doc: fix typos

Fix small typos in various documentations.

docs.dist/tutorial-basics/create-a-document.md

@@ -26,7 +26,7 @@ A new document is now available at `http://localhost:3000/docs/hello`.
 
 Docusaurus automatically **creates a sidebar** from the `docs` folder.
 
-Add metadata to customize the sidebar label and position:
+Add metadatas to customize the sidebar label and position:
 
 ```md title="docs/hello.md" {1-4}
 ---