Update package

## Changes(major+, minor*, fix-)

Update some scripts*
Introduce new APIs*
Update demo scene*
Update readme-

Update package

## Changes(major+, minor*, fix-)

Replace direct asset copying with `.unitypackage` import system for `Elements/` folder*

Context menu for forcefully importing the package's elements initially or during any updates*

Fix GUID conflicts when updating the package-

Refactor editor script-

Update docs-

Initial release

## Changes

Initial release for v1.0.0