I've used the following script (adding and subtracting specific warnings as needed) for the games I'm working on. Anyone should feel free to use this and edit it as they choose, no credit needed:
Safety
This game includes themes of fear, isolation, suspense, despair, violence, and death.
Read and play with caution, keeping in mind that you can take a break or stop completely at any time. Your mental health is important, and this is just a game.
This game is designed to make success very difficult and very unlikely. It is meant to be challenging and harrowing and emotional. If that doesn't sound fun to you, that's absolutely fine.
Remember that you can change, ignore, rewrite or abandon any part of this game that you want.