[aat.feat] Rework API and implementation

Fixes https://github.com/harfbuzz/harfbuzz/pull/1346
diff --git a/docs/harfbuzz-docs.xml b/docs/harfbuzz-docs.xml
index 66a64d8..2735338 100644
--- a/docs/harfbuzz-docs.xml
+++ b/docs/harfbuzz-docs.xml
@@ -113,6 +113,11 @@
       </chapter>
 
       <chapter>
+        <title>Apple Advanced Typography API</title>
+        <xi:include href="xml/hb-aat-layout.xml"/>
+      </chapter>
+
+      <chapter>
         <title>Integration API</title>
         <xi:include href="xml/hb-coretext.xml"/>
         <xi:include href="xml/hb-ft.xml"/>