I will add a brief warning to the itch pages, as it's now been formally requested. That said, I think the danger in such cases, while real, has been somewhat misunderstood and exaggerated over time. The Pokemon episode that put the issue on most people's radar, "Dennō Senshi Porygon", for example, resulted in the hospitalization of some 600 people (a real issue), but no deaths, and that episode is the WORST POSSIBLE scenario. To the best of my knowledge, there has NEVER been a death tied to a seizure caused by photosensitive epilepsy. Seizures are still bad enough on their own of course, and CAN be fatal, so sure, I'll put a notice. But I geniunely don't believe the mild flash effects in the games pose any risk to anyone, sensitive or otherwise. If I did, I wouldn't post a warning, I'd just leave them out.
For clarity however: CS and GT hypno effects sometimes include a MILD, SINGLE flash effect in ONE color. Occasionally, this may be strung together into as many as three or four, but somewhat spaced out in time. In contrast, the pokemon episode had a rapid STROBE effect of two colors that went on for several seconds. I'm NOT photosensitive, and even I find it kind of sickening to watch.