Allow critical battery power level to go beyond 20%

Right now, the warning for low battery can only occur at 20% or lower. This is noted in the docs, but isn't obvious to a user, as a number above 20 will just be clamped with no notification. Ideally the user would be made aware of the limit. Furthermore, I think it would be good to remove the limit or at least up it to something 50%. I don't see why warning at 25% shouldn't be allowed for example, and it's something I'd like to try personally, as my laptop battery decays.

Here's a screenshot of the specific UI section I'm referring to:

Thanks!