doc: add entry for AsyncHook class

fixes: #31661

PR-URL: #31865
Fixes: #31661
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/async_hooks.md

@@ -170,6 +170,11 @@ provided by AsyncHooks itself. The logging should then be skipped when
 it was the logging itself that caused AsyncHooks callback to call. By
 doing this the otherwise infinite recursion is broken.
 
+### Class: `AsyncHook`
+
+The class `AsyncHook` exposes an interface for tracking lifetime events
+of asynchronous operations.
+
 #### `asyncHook.enable()`
 
 * Returns: {AsyncHook} A reference to `asyncHook`.