To cite STV in publications use:
Jay Emerson (2022). STV: Single Transferable Vote Counting. Department of Statistics, Yale University, New Haven, CT. Work in Progress, https://github.com/jayemerson/STV.
You are probably just citing the package at this point.
Corresponding BibTeX entry:
@Manual{, title = {STV: Single Transferable Vote Counting}, author = {{Jay Emerson}}, organization = {Department of Statistics, Yale University}, address = {New Haven, CT}, year = {2022}, note = {Work in Progress}, url = {https://github.com/jayemerson/STV}, }