Add classic "Welcome" intro
This is (also) to address the review from bdach about StorageManager initialising a default value that gets overwritten upon migration anyway.
Also changes the class accessor from internal to public
Update framework
Fix editor drag selection not continuing to select unless the mouse is moved
Fix exception when dragging after deleting object
Don't activate run tool window on rider run
Fix player not exiting immediately on Alt-F4
Bump ppy.osu.Game.Resources from 2020.602.0 to 2020.622.1
Bumps [ppy.osu.Game.Resources](https://github.com/ppy/osu-resources) from 2020.602.0 to 2020.622.1. - [Release notes](https://github.com/ppy/osu-resources/releases) - [Commits](https://github.com/ppy/osu-resources/compare/2020.602.0...2020.622.1) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>