Publish Linux, macOS, and Windows quick starts

[sharifsalah]

Publish a Quick start based on the OpenCue sandbox:

https://github.com/AcademySoftwareFoundation/OpenCue/tree/master/sandbox

[sharifsalah]

The macOS and Linux quick starts are now published. Next step is to link to them prominently from the landing page.

[sharifsalah]

Updated the quick starts with steps to run a simple shell job. Still working on adding a link from the landing page.

[sharifsalah]

We should also add a Windows version of the quick start