Add PKNER

## Adding a Dataset
- **Name:** PKNER
- **Description:**  This work addresses this gap by introducing novel corpora and language models specifically designed for effective NER of pharmacokinetic parameters.
- **Task:** NER
- **Paper:** https://www.nature.com/articles/s41598-024-73338-3
- **Data:** https://github.com/PKPDAI/PKNER/tree/main
- **License:** MIT

