Question: who sings the theme song for the outlander series
[{'answer': 'Raya Yarbrough', 'provenance': [{'wikipedia_id': '990400', 'title': 'The Skye Boat Song', 'start_paragraph_id': 29, 'start_character': 96, 'end_paragraph_id': 29, 'end_character': 110, 'bleu_score': 1.0, 'section': 'Section::::Recording history and covers.:21st Century.\n'}]}, {'provenance': [{'wikipedia_id': '990400', 'title': 'The Skye Boat Song', 'start_paragraph_id': 29, 'start_character': 0, 'end_paragraph_id': 29, 'end_character': 225, 'bleu_score': 0.953991849837532, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5539746699919530280}, 'section': 'Section::::Recording history and covers.:21st Century.\n'}]}]