use index.md not index.html

Author: hectorsector

responses/01_update-index.md

@@ -4,7 +4,7 @@ Great job! Now that GitHub Pages is enabled, you can view your website here: {{
 
 You can customize your homepage by adding content to either an `index` file or the `README.md` file. GitHub Pages first looks for an `index` file. If an `index` file is found, GitHub Pages uses the content in the file to create the homepage. If an `index` file isn’t found, it uses the `README.md` to create the homepage.
 
-Your repository has an `index.html` file so we can update it to include your personalized content.
+Your repository has an `index.md` file so we can update it to include your personalized content.
 
 ### :keyboard: Activity: Create your homepage