feat: Calculate width/height of canvas based on container dimensions (".excalidraw" selector) & remove props width & height (#3379)

* Remove width/height from the ".excalidraw" container so it will sized automatically.
* updated all ref calculation to ".excalidraw" instead of parent since now ".excalidraw" will get resized
* Remove props width/height as its not needed anymore.
* Resize handler is also not needed anymore.
* Position absolute canvas due to #3379 (comment)

* move css to style and remove one extra rerendering

* factor out mock logic for test

* set height, width so as to avoid unnecessary updates of regression snap

* better mock

* better type checking and omit width,height from getDefaultAppState and also restore

* revert

* default to window dimensions in constructor

* update docs

* update

* update

* tweaks

src/index-node.ts

@@ -63,6 +63,8 @@ const canvas = exportToCanvas(
     ...getDefaultAppState(),
     offsetTop: 0,
     offsetLeft: 0,
+    width: 0,
+    height: 0,
   },
   {
     exportBackground: true,