Update (version 28.5 + 28.6)

- Added support for animated skins (please report bugs and broken skins in the comments/forum)
- Added active mods to ranking/results screen
- Added avg error to Unstable Rate tooltip
- Added support for HitCirclePrefix in skin.ini
- Converted hardcoded hitwindow timing values into ConVars (osu_hitwindow_...)
- Fixed random vertexbuffer corruptions with shrinking sliders enabled (white flashes/blocks/triangles/lines, distorted slider bodies)
- Fixed animated skin elements of the default skin incorrectly overriding user skins