Implement whiteboard sync (#33)

* Create Notes & Whiteboard components and classes

* sync changes

* add fabricjs whiteboard

* fix imports

* add zoom and panning to whiteboard

* improve code

* remove unused var

* improve code

* emit websocket events for whiteboard changes

* remove console log

* load whiteboard if saved one exists

* add erase function to whiteboard canvas

* fix prettier

* change whiteboard sync implementation

* revert package.json

* add option to download canvas as png

* fix load empty canvas

* remove this in functions

* Revert "remove this in functions"

This reverts commit 7605e7e8fd54a6e20407dc4ce89139680900f78b.

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Co-authored-by: Florian Raith <florianraith00@gmail.com>