Release Notes for 421

Added more microprofiler labels for work in Kernel::stepWorld:

• BuoyancyAccumulator::computeForce
• Humanoid::computeForces
• KernelJoint::computeForces
• copyCollisionConnectors

Standalone Plugin development is now available to third party developers.

ScrollingFrames now scroll smoothly when scrolled via the mouse wheel.

Fixed a benign CoreScript error in NotificationScript

New publish flow success screen will display a valid game icon and game name

Fix error in some game joins resulting in the following in the dev console:

16:50:19.088 - BlackFrame is not a valid member of ScreenGui 16:50:19.088 - Script 'LoadingScript', Line 370 16:50:19.088 - Stack End 16:50:19.089 - Disconnected event because of exception