docs: create section for sidebar config

Author: machow

docs/get-started/sidebar.qmd

@@ -23,6 +23,15 @@ with a [Quarto sidebar configuration](https://quarto.org/docs/websites/website-n
 The Quarto [`metadata-files` option](https://quarto.org/docs/projects/quarto-projects.html#metadata-includes) ensures
 it's included with the configuration in `_quarto.yml`.
 
+Here is what the sidebar for the [quartodoc reference page](/api) looks like:
+
+<div class="sourceCode">
+<pre class="sourceCode yaml"><code class="sourceCode yaml">{{< include /api/_sidebar.yml >}}
+</code></pre>
+</div>
+
+## Customizing the sidebar
+
 `sidebar` can also accept additional [sidebar options from the choices available in Quarto](https://quarto.org/docs/websites/website-navigation.html#side-navigation). These options are passed directly to Quarto, and can be used to customize the sidebar's appearance and behavior, or include additional content. 
 
 When using a dictionary for `sidebar`, use `file` to specify the sidebar file (defaults to `_quartodoc-sidebar.yml` if not provided). You can also provide additional content in the sidebar. Tell quartodoc where to include your package documentation in the sidebar with the `"{{ contents }}"` placeholder.
@@ -43,10 +52,3 @@ quartodoc:
       - text: "Basics"
         href: basics-summary.qmd
 ```
-
-Here is what the sidebar for the [quartodoc reference page](/api) looks like:
-
-<div class="sourceCode">
-<pre class="sourceCode yaml"><code class="sourceCode yaml">{{< include /api/_sidebar.yml >}}
-</code></pre>
-</div>