Fix documentation warning

In wasm, the documentation eed to be repeated

sixtyfps_runtime/corelib/tests.rs

@@ -98,6 +98,8 @@ cfg_if::cfg_if! {
         }
 
         #[macro_export]
+        /// This macro allows producing debug output that will appear on stderr in regular builds
+        /// and in the console log for wasm builds.
         macro_rules! debug_log {
             ($($t:tt)*) => ($crate::tests::log(&format_args!($($t)*).to_string()))
         }