enable ScratchJr to run on MacOS

[chrisgarrity]

ScratchJr cannot take advantage of the fact that new Macs will be able to run iOS apps.

Specific errors reported by Apple that prevent ScratchJr from being available on the Mac App Store:

• App cannot be used as intended. It includes jailbreak detection and multitouch requirements not addressed by Touch Alternatives.

A big issue is that it relies entirely on touch without any keyboard or mouse input. Updating to the latest Xcode beta and trying to build should also provide feedback about what's incompatible.

Resources:

• Running iOS apps on MacOS
• Adapting iOS code to run in the MacOS environment
• Mac Catalyst

It is not yet said that that it supports pc and mac try to run in you ios mobile or android

[yueyuzhao]

We add mouse support via https://github.com/LLK/scratchjr/pull/425 and some issues requires mouse support but I have no Chromebook to test, so I decide to implement this first.

[deepankarmalhan]

Make an epic and leave it for now.