feat: Builder accepts out_index argument

Author: machow

quartodoc/autosummary.py

@@ -142,6 +142,7 @@ def __init__(
         dir: str = "reference",
         title: str = "Function reference",
         renderer: "dict | Renderer | str" = "markdown",
+        out_index: str = None,
     ):
         self.validate(sections)
 
@@ -159,6 +160,9 @@ def __init__(
 
         self.renderer = Renderer.from_config(renderer)
 
+        if out_index is not None:
+            self.out_index = out_index
+
     def build(self):
         """Build index page, sphinx inventory, and individual doc pages."""