To cite package ‘SRTtools’ in publications use:

  Chen J (2019). _SRTtools: Adjust Srt File to Get Better Experience
  when Watching Movie_. R package version 1.2.0,
  <https://github.com/chihangchen/srttools>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {SRTtools: Adjust Srt File to Get Better Experience when Watching Movie},
    author = {Jim Chen},
    year = {2019},
    note = {R package version 1.2.0},
    url = {https://github.com/chihangchen/srttools},
  }