Add pipeline tag and license

This PR improves the model card by adding the `pipeline_tag` and `license` metadata. The `pipeline_tag` is set to `text-to-image`, enabling users to easily discover this model when searching for text-to-image models on the Hub. The license is added based on the information found in the Github README. A link to the GitHub repository is also included to give users access to the code and more detailed information about the model.

README.md

@@ -1,6 +1,8 @@
 ---
 library_name: transformers
+pipeline_tag: text-to-image
 tags: []
+license: apache-2.0
 ---
 
 # Model Card for Ti*k*Zero+ (10b)