Correct the published metadata

Adds library_name to the model card, and pipeline_tag where it was missing.
Brings the config and card licenses into agreement, and repairs the variant
declarations that did not match the files actually published here.

README.md

@@ -3,6 +3,7 @@ license: mit
 pipeline_tag: text-generation
 tags:
 - executorch
+library_name: executorch
 ---
 
 # Introduction