Add Sburban Cartdown as a track

[towerofnix]

https://hsmusic.wiki/flash/sburban-cartdown/

"Sburban Cartdown" refers to a 2019 animation by Shadok, which features a 2010 or earlier track by Erik Scheele by the same name. Shadok's given credits are as below:

Music is "Sburban Countdown" by Mark Hadley & Michael Guy Bowman, and sentence mixing by Erik "Jit" Scheele.

But these credits don't indicate Sburban Cartdown as its own much earlier track.

Add Sburban Cartdown as its own track (More Homestuck Fandom) with a reference to Sburban Coutndown, of course; replace which track is featured in the animation; and remove Erik Scheele as a direct contributor to the flash.

Courtesy Sgeo via #music-discussion and Tangle via #music-discussion / #issuefication-zone.