fix: filter out duplicate plugins

[atomiks]

• Addons were .concating defaultProps.plugins unnecessarily since tippy() does it.
• Duplicate plugins should be filtered out at createTippy() for extra safety.

Most exported plugins when duplicated don't cause issues but make performance worse.

unique() could use [...new Set(plugins)] which is faster I think, but I'm not sure of how well-supported it is, best to use this one?

[atomiks]

Also something odd is the linter is not longer complaining about lack of return type for callback functions like .filter() (which is way less noisy and better, maybe we can remove all of them in another PR).