feature: Load embedded images from excalidraw files

This was contributed by @lionelhorn. Approach is to wait for
the "update" message that has the embedded files then create
`initialData` with the files and only then render the
Excalidraw component.

Mobx is used for state management replacing react `useState`.
Which is easier to get the code a bit cleaner code
than passing the setters of `useState` to the bridge.

Co-authored-by: Lionel <dev@lionelhorn.com>

Author: bric3

excalidraw-assets/package.json

@@ -12,6 +12,8 @@
     "@types/react": "^18.0.0",
     "@types/react-dom": "^18.0.0",
     "awesome-debounce-promise": "^2.1.0",
+    "mobx": "6.13.1",
+    "mobx-react": "9.1.1",
     "react": "^18.0.0",
     "react-app-rewired": "^2.1.8",
     "react-dom": "^18.0.0",