Histcite-python

- Support `plain text format` from web of science.

- Add new dependency [refparse](https://github.com/doublessay/refparse). It is lightweight but powerful.
- Improve matching method. Now could well identify citation relationships involving conference papers from web of science.
- Rewrite most modules and remove redundant code. Now it has a clear structure and is easy-understanding.
- **Attention: Please use the newest `demo.ipynb`.**

Now could export more sheets for wos source:
- Institution with Subdivision
- Country
- Corresponding Authors

Thanks for nkh0472 Pull request(8)

- Fix the error triggered by the `BP` type 6

- Add `histcite.show_versions()` function to help issue report

- Support Python 3.12
- Enhance test coverage to 86%
- Drop API document
- Rename variables
- `doc_index` -> `doc_id`
- `citation_relationship` -> `citation_relation`