Q2-itsxpress

- Fixed single end bug where Single end was always False
- Added compatibility to newer Vsearch version
- Updated to pyproject.toml config file
- Removed interleaved option (if needed, see reformat.sh in the bbmap package)

**Full Changelog**: https://github.com/USDA-ARS-GBRU/q2_itsxpress/compare/v1.8.0...v1.8.1

* Added support to reversed primers.
* Added error handling for empty input files

* Updates to bring github version and pip version back in line.
* Increased the minimum version of ITSxpress required to 1.7.2 so that the latest bug fix is included

Changes to the qiime data types being used for better error handling.

Manifest file fixed to include citations.bib

* added citations.bib file that was missing in 1.7.0