How to stop screen dimming while reading?

I’m trying to read something on my iPhone. I lay it down on the table at the coffee shop while I eat and periodically tap the screen to scroll down. The screen keeps dimming automatically before I get to the bottom of the page, which is super annoying and makes it so I can’t really read on the phone in this situation. I can change the battery settings to lock after 1 minute or 2 but I want to preserve battery life and don’t want to forget to turn it back. I can’t hold the phone in my hand while reading because it is heavy and I’m using my hands to eat. How can I stop the screen from dimming? The iPhone gets zillions of user interactions right- it’s amazing - but this one common use case is totally broken. If the system can’t figure out what I’m doing automatically I’d like there to be a widget in the control center for “Reading mode” or something that temporarily increases the dimming delay.