Flatten some structures.

src/wasm/paragraph.rs

@@ -16,6 +16,7 @@ use crate::wasm::WasmAstNode;
 #[serde(rename = "paragraph")]
 pub struct WasmParagraph<'s, 'p> {
     pub(crate) standard_properties: WasmStandardProperties,
+    #[serde(flatten)]
     pub(crate) additional_properties: AdditionalProperties<'s, 'p>,
     pub(crate) children: Vec<WasmAstNode<'s, 'p>>,
 }