The PHPSW website is one of the earliest Tailwind CSS projects I did, at least that I can remember.
Tailwind CSS was added to the project on the 13th of November, 2017 (almost 7 years ago), and the yarn.lock file shows the version as 0.1.6.
0.1.0 was only released on the 1st of November, and 1.0.0 wouldn't be released until May 2019.
Here's a photo from an evening when Dave, Kat and I were working on it at the Lamp Bristol office.