[Suggestion] Separate scrollfactors for horizontal and vertical parallax scrolling

[villager103]

The way parallax scrolling behaves with vertically-scrolling levels works fine, however it has some side effects that ruin some background styles.

For instance, if you have a parallax scrolling background on a vertical level, but the background doesn't loop vertically, you have to make your level ridiculously tall otherwise the bottom of the background won't appear, among other issues.

I propose separating horizontal and vertical scrollfactors, so you can have parallax scrolling be different on each axis, for example, have it parallax scroll horizontally, but not vertically.