docs: restructure documentation into MkDocs Material site

docs/reference/api/titles.md

@@ -0,0 +1,14 @@
+# Titles API
+
+Auto-generated reference for the title model: Movies, Series/Episodes, and Music/Albums/Songs.
+A service returns one of these collections from its title lookup. See
+[Creating a Service](../../dev/creating-a-service.md).
+
+::: unshackle.core.titles
+    options:
+      show_root_heading: false
+      show_source: false
+      members_order: source
+      heading_level: 2
+      filters:
+        - "!^_"