docs: add documentation for mo.outline widget (#6468)

Author: mscolnick

docs/api/layouts/index.md

@@ -18,6 +18,7 @@ them but just render their children in a certain way.
 | [`marimo.lazy`][marimo.lazy] | Lazy load content |
 | [`marimo.left`][marimo.left] | Left-align content |
 | [`marimo.nav_menu`][marimo.nav_menu] | Create navigation menus |
+| [`marimo.outline`][marimo.outline] | Display table of contents outline |
 | [`marimo.plain`][marimo.plain] | Display content without styling |
 | [`marimo.right`][marimo.right] | Right-align content |
 | [`marimo.routes`][marimo.routes] | Create page routing |

docs/api/layouts/outline.md

@@ -0,0 +1,24 @@
+# Outline
+
+/// marimo-embed
+
+```python
+@app.cell
+def __():
+    mo.md("# Header 1")
+    return
+
+@app.cell
+def __():
+    mo.md("## Header 2")
+    return
+
+@app.cell
+def __():
+    mo.outline(label="Table of Contents")
+    return
+```
+
+///
+
+::: marimo.outline

mkdocs.yml

@@ -232,6 +232,7 @@ nav:
           - Json: api/layouts/json.md
           - Justify: api/layouts/justify.md
           - Lazy: api/layouts/lazy.md
+          - Outline: api/layouts/outline.md
           - Plain: api/layouts/plain.md
           - Routes: api/layouts/routes.md
           - Sidebar: api/layouts/sidebar.md