fix api index

docs/api/index.md

@@ -1,3 +1,5 @@
-# Reference
+# API
 
-A reference to the Textual public APIs.
+This is a API-level reference to the Textual API. See the links on the left (or in the burger menu) for each module, where you can drill down to a class or method.
+
+If you are new to Textual, you may want to read the [tutorial](./../tutorial.md) or [guide](../guide/index.md) first.

mkdocs.yml

@@ -98,6 +98,7 @@ nav:
       - "widgets/static.md"
       - "widgets/tree_control.md"
   - API:
+    - "api/index.md"
     - "api/app.md"
     - "api/button.md"
     - "api/color.md"
@@ -107,7 +108,6 @@ nav:
     - "api/footer.md"
     - "api/geometry.md"
     - "api/header.md"
-    - "api/index.md"
     - "api/message_pump.md"
     - "api/message.md"
     - "api/pilot.md"