docs: Add brand-yml to interlinks inventories

Author: gadenbuie

docs/_quarto.yml

@@ -44,3 +44,5 @@ interlinks:
       url: https://matplotlib.org/stable/
     python:
       url: https://docs.python.org/3/
+    brand-yml:
+      url: https://posit-dev.github.io/brand-yml/