feat: unpublish author pages in the default tpl

Based on feedback from users creating personal sites and not wanting to publish dedicated page for each author.

But keep publishing author pages in the demo for now.

content/authors/_index.md

@@ -0,0 +1,9 @@
+---
+# To publish author profile pages, remove all of the `_build` and `cascade` settings below.
+_build:
+  render: never
+cascade:
+  _build:
+    render: never
+    list: always
+---