Easier AttributeSet creation

[Yamakaky]

Currently, to create an AttributeSet, we need to do a list on .insert or a loop. It would be nice to be able to do it via a constructor, for example AttributeSet::with_values(&[Key::BTN_A, Key::BTN_B]).

[StephanvanSchaik]

It is currently possible to create an AttributeSet from an array/iterator like in the following example:

let keys = AttributeSet::from_iter([Key::BTN_A, Key::BTN_B]);

[Yamakaky]

Thanks, maybe it was added in the mean time !