Add a pinch to paint example scene to the preview package

[JuliaRonnebergerUL]

Summary

Adding a minimal version of paint to the preview package to show off the pinch detector, the pinch cursor and paint ribbons

Contributor Tasks

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• [ ] Pair review with a member of the QA team.
• [x] Add any release testing considerations to the MR for the next release.
• [x] Consider any licensing/other legal implications for this MR e.g. notices required by any new libraries.
• [x] If this MR closes a Jira issue, make sure the fix version on the JIRA issue is set to the correct one.

Reviewer Tasks

Add any instructions or tasks for the reviewer such as specific test considerations before this can be merged.

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• [ ] Code reviewed.
• [x] Non-code assets e.g. Unity assets/scenes reviewed.
• [ ] Checked and agree with release testing considerations added to MR for the next release.

Closes JIRA Issue

Closes AUR-47

[MaxPalmer-UH]

@JuliaRonnebergerUL Can we comment public methods please? Also can you draft documentation for this, like the Core examples? I know it's preview but would be great to get the documentation done now while it's still fresh. Thanks.

[MaxPalmer-UH]

@JuliaRonnebergerUL thanks for the changes. Looking really nice. One thing to put in the docs is an explanation of how to switch pinch to paint to the left hand. Happy to merge.