Move metadata extensions page to creating extensions section (#1733) (#1737)

(cherry picked from commit 23ce59f)

Co-authored-by: Charlotte Wickham <[email protected]>

Author: github-actions[bot]

_quarto.yml

@@ -449,8 +449,6 @@ website:
               href: docs/extensions/listing-formats.qmd
             - text: "Revealjs Extensions"
               href: docs/extensions/listing-revealjs.qmd
-            - text: "Metadata Extensions"
-              href: docs/extensions/metadata.qmd
             - docs/extensions/managing.qmd
         - "---"
         - section: docs/extensions/creating.qmd
@@ -475,6 +473,8 @@ website:
             - docs/extensions/formats.qmd
             - docs/extensions/revealjs.qmd
             - docs/extensions/project-types.qmd
+            - text: "Metadata Extensions"
+              href: docs/extensions/metadata.qmd
             - docs/extensions/starter-templates.qmd
 
     - id: reference