chore: update navigation settings in index.qmd

Set page-navigation and toc to false for improved document structure.

Author: mcanouil

docs/get-started/index.qmd

@@ -1,6 +1,8 @@
 ---
 title: "Get Started"
 subtitle: "Install gribouille and render your first plot."
+page-navigation: false
+toc: false
 ---
 
 ## Prerequisites