Handle outside click for story creator url popover

[ryprice]

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Description

Fixes #6207

Currently, the story creator url popover does not close on outside click. This change sets up a click handler, following the pattern used for the similar background color picker, use handleOutsideClick to close the url popover.

Testing

Tested on macOS 10.15.7. No new test cases written.

• Verified on outside click closes url popover. (note it causes the text editor to open, but this is not a new issue)
• Verified esc key closed the url popover.
• Verified clicking on text in edit mode places text cursor where mouse click occurred, and closes url popover. This issue was noted in the previous Close story editor's link preview on outside click #6209.
• Verified esc and outside click work as expected on color popover.
• Verified I could add a URL to the story.

closeonoutsideclick.mp4

[devbks]

I've added some thoughts for some readability and minor performance improvements.

[devbks]

Can this cleanup callback be a function outside of useEffect with useCallback ?
I think that will make this code more readable and cleaner.