Add an option that makes holding shift optional to change volume using scroll

[ParticleCore]

User requested feature, and should be simple enough to implement.

This option will allow users to keep the previous behavior of changing video volume using scroll without having to hold the shift key at the same time, but the added limitation is they will only be able to do it while the mouse is on the video, which is a limitation from the previous implementation too.

[ParticleCore]

The feature is working correctly, and I decided to group all three under one section to hopefully minimize confusion:

Both the shift and steps options are linked to the scroll option, if the scroll is turned off then the other become disabled.