Implement addition for OwnedLiterals.

src/bin.rs

@@ -8,6 +8,7 @@ use renderer::compile_template;
 use renderer::CompileError;
 use renderer::ContextElement;
 use renderer::DustRenderer;
+use renderer::IceResult;
 use renderer::IntoContextElement;
 use renderer::Loopable;
 use renderer::RenderError;
@@ -387,6 +388,10 @@ impl CompareContextElement for serde_json::Value {
             _ => panic!("Unimplemented comparison type."),
         }
     }
+
+    fn math_add<'a>(&self, other: &dyn ContextElement) -> Option<IceResult<'a>> {
+        todo!()
+    }
 }
 
 #[derive(Debug)]