add new example

Author: molpopgen

Cargo.toml

@@ -56,3 +56,7 @@ rustdoc-args = ["--cfg", "doc_cfg"]
 # Not run during tests
 [[example]]
 name = "tree_traversals"
+
+[[example]]
+name = "json_metadata"
+required-features = ["derive"]

examples/json_metadata.rs

@@ -0,0 +1,3 @@
+fn main() {
+    todo!()
+}