To cite package ‘plotly’ in publications use:

  C. Sievert. Interactive Web-Based Data Visualization with R, plotly,
  and shiny. Chapman and Hall/CRC Florida, 2020.

A BibTeX entry for LaTeX users is

  @Book{,
    author = {Carson Sievert},
    title = {Interactive Web-Based Data Visualization with R, plotly, and shiny},
    publisher = {Chapman and Hall/CRC},
    year = {2020},
    isbn = {9781138331457},
    url = {https://plotly-r.com},
  }