FRE-600: Fix code review blockers

- Consolidated duplicate UndoManagers to single instance
- Fixed connection promise to only resolve on 'connected' status
- Fixed WebSocketProvider import (WebsocketProvider)
- Added proper doc.destroy() cleanup
- Renamed isPresenceInitialized property to avoid conflict

Co-Authored-By: Paperclip <noreply@paperclip.ing>

node_modules/level-packager/CONTRIBUTORS.md

@@ -0,0 +1,12 @@
+# Contributors
+
+| Name                 | GitHub                                                 | Social                                                          |
+| :------------------- | :----------------------------------------------------- | :-------------------------------------------------------------- |
+| **Lars-Magnus Skog** | [**@ralphtheninja**](https://github.com/ralphtheninja) | [**@ralph@social.weho.st**](https://social.weho.st/@ralph)      |
+| **Vincent Weevers**  | [**@vweevers**](https://github.com/vweevers)           | [**@vweevers@twitter**](https://twitter.com/vweevers)           |
+| **Julian Gruber**    | [**@juliangruber**](https://github.com/juliangruber)   | [**@juliangruber@twitter**](https://twitter.com/juliangruber)   |
+| **Rod Vagg**         | [**@rvagg**](https://github.com/rvagg)                 | [**@rvagg@twitter**](https://twitter.com/rvagg)                 |
+| **Alex Potsides**    |                                                        |                                                                 |
+| **Andrew Kelley**    | [**@andrewrk**](https://github.com/andrewrk)           |                                                                 |
+| **Deian Stefan**     | [**@deian**](https://github.com/deian)                 |                                                                 |
+| **Matteo Collina**   | [**@mcollina**](https://github.com/mcollina)           | [**@matteocollina@twitter**](https://twitter.com/matteocollina) |