Add `open` prop to Popup types (and docs)

[evantayloryates]

Feature Request

Problem description

The Popup component documentation doesn't include the open prop in the prop list. I looked at the Popup type declaration file and it doesn't seem to be included.

Proposed solution

This might be as simple as adding the open prop to the Popup type declaration file. If that's the case, I can try to open up a PR for this fix. Would like to make sure there are no side effects though so figured I'd start with an issue to flag it

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