What has a cooler got to do with sous-vide cooking?
Coolers (chilly bins) are ideal sous-vide cooking vessels as they are well insulated, and thus conserve energy and avoid temperature varying across the water bath.

Most sous-vide cooking happens at less than 80°C (176°F), so the plastic will stand up fine.

Many commercial clip on sous-vide cookers are only suitable for fish tank style containers (thin walled). These tanks look pretty, but waste a lot of energy, and can struggle to keep the same temperature throughout all the water. An interchangeable clip, or wide reach clip is more useful for coolers or other insulated vessels.

Specifically with the Chefsteps Joule sous-vide cooker: it seems to have a powerful magnet in its foot, so if you place a sheet of coated steel on the bottom of your cooler, you won't even need a clip.