Add PlexTrac to ADOPTERS.md
- [Novolabs](https://novolabs.com)
- [Paybase](https://paybase.io/)
- [PlayStudios Asia](https://www.playstudios.asia)
+- [PlexTrac](https://plextrac.com)
- [PriceKinetics (GVC Australia)](https://www.pricekinetics.com.au/)
- [Projector](https://projector.com)
- [Purdue University Global](https://www.purdueglobal.edu/)
