InputEventScreenTouch has unhelpful descriptions

**Your Godot version:**
4.1.1

**Issue description:**
The descriptions of some properties provide no additional information than the properties names themselves, this is
especially true for the `cancelled` property.
I don't understand when cancelling a touch input means, what action do i need to do with my finger/pen to "cancel" it?
It would also be nice to know how indexes are assigned for the `index` property. (I need to know this because i'm using the value -1 in my code to represent no active touch input, and i would like to be sure that indexes can never be negative)

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/classes/class_inputeventscreentouch.html