Add criterion-metadata.json manually

Author: moreal

_data/criterion-metadata.json

@@ -0,0 +1,5 @@
+{
+  "generated_at": "2026-01-07T14:06:57Z",
+  "rustpython_commit": "c490a357fd54d578ae92681b8b1b4bae5006d843",
+  "rustpython_ref": "main"
+}