refactor: rename DTree to DValue

site/doc/pages/component_render.txt

@@ -1,5 +1,5 @@
 :sig
-void component_render(String name, [DTree props], [Request& context])
+void component_render(String name, [DValue props], [Request& context])
 
 :see
 >ob
@@ -24,7 +24,7 @@ Use `component_render()` when you want to write component output directly from C
 ## Example
 
 ```cpp
-DTree props;
+DValue props;
 props["body"] = "Hello";
 
 component_render("components/card:BODY", props, context);