Playfield border for osu!catch

[Tenexxt]

Self-explainatory. Would work like it does in !Std, but for !CtB.
This also wouldn't need that much work, since a cornered playfield border is already available in the !CtB editor, so there would only need to be added a whole one.

Here's how it looks in the editor:

Why should this be added?

As a person who also plays !CtB, sometimes when there are objects on the edge of the playfield, i don't know how i can play around those edges because i don't know if there is a wall close or not (Because the walls are invisible in case you forgot). If i knew where there is a wall, i would know if i can safely dash on full force or just go for the wall, rather if i have to guess for how long can i still go on the sides. Also it would look cool IMO.