What type of trigger warnings are we talking about? Because that word now means not exactly what it should mean.
https://en.wikipedia.org/wiki/Trauma_trigger
It now means that it will offend someone, like the overyl woke or other kinds of bigotted people that bully people into compliance. Since offending is part of what makes art art, trigger warnings are kinda dubious. Ever seen one in front of a painting or a movie? I remember a disclaimer in front of Dogma. Done for laughs. But otherwise? As for games, was there a trigger warning for one of the scenes in Skyrim in the intro shortly before the dragon attacked? I think not.
Usually an age rating would suffice to do what people think a trigger warning should do.
That being said, we are talking indie games here, so no rating board and small amount of negative reviews can seriously harm a game. People can react quite hateful to certain things, if they come unexpected.
So they should either expect them by the genre, theme, description or even the game tags. If you have content that people have strong reactions to, you might wanna check if that content is typical for the type of game and decide if a warning were a spoiler or could help prevent 1 star ratings of disgruntled players. The medical angle is a bit far fetched imho (also think about my point about trigger warnings for other content. You would need one in front of every movie if that were a thing). Unless you advertise a kids game and continue to traumatize them, nahh, as has been explained, true triggers can be anything and the other kind are not medical. Flashing lights are medical and should be warned, this stuff is real. But offending people?