Background sprites are %100 opaque instead of %99 opaque

A rare bugfix when OnApplicationQuit is canceled by Application.wants…

…ToQuit (closed yasirkula#19)

Bumped package version

Added new Input System support (requires manual modifications, see do…

…cumentation)

- Added OnPanelClosed and OnTabClosed events to PanelNotificationCent…

…er. Once these events are populated, close buttons will show up at the top right corner of each panel and/or tab (see the documentation)(closed yasirkula#6)

- Added OnTabCreated and OnTabDestroyed events to PanelNotificationCenter

Bumped version

Added OpenUPM instructions

- To listen for pointer events, NonDrawingGraphic is now used instead…

… of an Image (results in slightly improved graphics performance)

- Fixed yasirkula#3