lit version wraperBounds incorrect (always at 0, 0)

[augonis]

Thanks for the tool.

In lit version Pancake.wrapperBounds always ends up with {x:0 y:0} because (at least in chrome) ResizeObserverEntry.contentRect always has x=0, y=0, which then throws off client-canvas coordinate transformations

For now I've patched the ResizeObserver callback to use getClientRects instead. Though ResizeObserver is likely not the right tool for the purpose.

protected firstUpdated(_changedProperties: PropertyValueMap<any> | Map<PropertyKey, unknown>): void {
    if (!this._wrapper) {
      return console.error('No wrapper found');
    }
    this.resizeObserver = new ResizeObserver((entries) => {
      //this.wrapperBounds = entries[0].contentRect;
      this.wrapperBounds = entries[0].target.getClientRects()[0]; 
    });
    this.resizeObserver.observe(this._wrapper);
  }

I can make a PR with this patch, or even work on better solution.