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/css/styles.scss

@@ -16,6 +16,8 @@
   bottom: 0;
   left: 0;
   right: 0;
+  height: 100%;
+  width: 100%;
 
   // serves 2 purposes:
   // 1. prevent selecting text outside the component when double-clicking or
@@ -45,6 +47,10 @@
     image-rendering: -moz-crisp-edges; // FF
 
     z-index: var(--zIndex-canvas);
+
+    // Remove canvas from document flow to avoid resizeObserver feedback loop
+    // (see https://github.com/excalidraw/excalidraw/pull/3379)
+    position: absolute;
   }
 
   &.theme--dark {