Test RL Environment badge precedence on registered ExtractBench

Adds only the `rl-environment` dataset-card tag to test its display alongside the existing official Benchmark registration. No Harbor export files are included.

The existing `eval.yaml`, dataset configuration, documents, and annotations are unchanged. Badge precedence remains to be checked after merge.

README.md

@@ -32,6 +32,7 @@ pretty_name: ExtractBench
 size_categories:
 - n<1K
 tags:
+- rl-environment
 - document-extraction
 - structured-extraction
 - information-extraction