docs: rename upgrading index to allow supporting navigation indexes

docs/getting-started/upgrading/index.md

@@ -1,6 +1,6 @@
 # Upgrading
 
-If your version of Dokku is pre 0.3.0 (check with `dokku version`), we recommend [a fresh install](/docs/getting-started/installation.md) on a new server.
+If your version of Dokku is pre 0.3.0 (check with `dokku version`), we recommend [a fresh install](/docs/getting-started/installation/index.md) on a new server.
 
 ## Security Updates
 

docs/networking/dns.md

@@ -65,7 +65,7 @@ If everything is working correctly, you should also be able to query for any oth
 
 If they all return your IP address, you have set DNS up properly for dokku.  You should also be able to `ssh root@myserver.example.tld` and access your server.
 
-Proceed with the setup instructions in the [installation documentation](/docs/getting-started/installation.md)
+Proceed with the setup instructions in the [installation documentation](/docs/getting-started/installation/index.md)
 
 ### Using the root of your domain (node-js-app.example.tld)
 

mkdocs.yml

@@ -38,6 +38,7 @@ theme:
   custom_dir: docs/_overrides
   favicon: assets/favicons/favicon-96x96.png
   features:
+    - navigation.indexes
     - navigation.instant
     - navigation.sections
     - navigation.tabs