Bias template/tutorial to use .mdx

packages/create-docusaurus/templates/shared/docs/tutorial-basics/congratulations.mdx

@@ -8,7 +8,7 @@ You have just learned the **basics of Docusaurus** and made some changes to the
 
 Docusaurus has **much more to offer**!
 
-Have **5 more minutes**? Take a look at **[versioning](../tutorial-extras/manage-docs-versions.md)** and **[i18n](../tutorial-extras/translate-your-site.md)**.
+Have **5 more minutes**? Take a look at **[versioning](../tutorial-extras/manage-docs-versions.mdx)** and **[i18n](../tutorial-extras/translate-your-site.mdx)**.
 
 Anything **unclear** or **buggy** in this tutorial? [Please report it!](https://github.com/facebook/docusaurus/discussions/4610)
 

packages/create-docusaurus/templates/shared/docs/tutorial-basics/create-a-blog-post.mdx

@@ -8,7 +8,7 @@ Docusaurus creates a **page for each blog post**, but also a **blog index page**
 
 ## Create your first Post
 
-Create a file at `blog/2021-02-28-greetings.md`:
+Create a file at `blog/2021-02-28-greetings.mdx`:
 
 ```md title="blog/2021-02-28-greetings.md"
 ---

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

@@ -7,7 +7,7 @@ sidebar_position: 1
 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.mdx` → `localhost:3000/foo`
 - `src/pages/foo/bar.js` → `localhost:3000/foo/bar`
 
 ## Create your first React Page
@@ -32,9 +32,9 @@ A new page is now available at [http://localhost:3000/my-react-page](http://loca
 
 ## Create your first Markdown Page
 
-Create a file at `src/pages/my-markdown-page.md`:
+Create a file at `src/pages/my-markdown-page.mdx`:
 
-```mdx title="src/pages/my-markdown-page.md"
+```mdx title="src/pages/my-markdown-page.mdx"
 # My Markdown page
 
 This is a Markdown page

packages/create-docusaurus/templates/shared/docs/tutorial-basics/markdown-features.mdx

@@ -10,7 +10,7 @@ Docusaurus supports **[Markdown](https://daringfireball.net/projects/markdown/sy
 
 Markdown documents have metadata at the top called [Front Matter](https://jekyllrb.com/docs/front-matter/):
 
-```text title="my-doc.md"
+```text title="my-doc.mdx"
 // highlight-start
 ---
 id: my-doc-id
@@ -22,7 +22,7 @@ slug: /my-custom-url
 
 ## Markdown heading
 
-Markdown text with [links](./hello.md)
+Markdown text with [links](./hello.mdx)
 ```
 
 ## Links
@@ -34,10 +34,10 @@ Let's see how to [Create a page](/create-a-page).
 ```
 
 ```md
-Let's see how to [Create a page](./create-a-page.md).
+Let's see how to [Create a page](./create-a-page.mdx).
 ```
 
-**Result:** Let's see how to [Create a page](./create-a-page.md).
+**Result:** Let's see how to [Create a page](./create-a-page.mdx).
 
 ## Images