OSX Drag to clone with command key(metaKey) instead of ctrlKey

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PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] The commit message follows our guidelines: https://github.com/CirclonGroup/angular-tree-component/blob/master/CONTRIBUTING.md#commit-message-guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

OSX 'ctrl + click' converts it into a right click action on OSX making 'drag to copy' impossible

Closes #

What is the new behavior?

Use CMD key captured as metaKey for OSX https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/metaKey

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information