Add an option to disable Linux middle-click paste

[micahscopes]

Release Notes:

• Added an editor setting to toggle Linux middle-click pasting (enabled by default)

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[micahscopes]

@cla-bot check

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[micahscopes]

On my laptop, scrolling sprinkles little pastes here and there. It's super annoying and has cost me many hours of focus.

[micahscopes]

@mrnugget thanks for the review. As far as I can tell I've made the changes you suggested.

[mrnugget]

Thank you!