move brand-mode under dark brand

Author: gordonwoodhull

docs/authoring/brand.qmd

@@ -109,6 +109,19 @@ brand:
   dark: dark-brand.yml
 ```
 
+#### Typst
+
+To choose a dark brand in Typst output use `brand-mode: dark`:
+
+```{.yaml filename="document.qmd"}
+---
+format:
+  typst:
+    brand-mode: dark
+---
+```
+
+
 ## Brand Elements
 
 The elements of **brand.yml** are specified in the documentation for the [**brand.yml** project](https://posit-dev.github.io/brand-yml/){.external}. 
@@ -663,13 +676,4 @@ theme:
 
 Learn more about how Quarto generates styles in [More About Quarto Themes](/docs/output-formats/html-themes-more.qmd).
 
-## Choosing light or dark brand in Typst
-
-If the document has [both light and dark brands](#dark-brand), use `brand-mode: dark` to produce a dark-background PDF that matches the dark brand of your website.
-
-``` yaml
-format:
-  typst:
-    brand-mode: dark
-```