Expand measureElement API for increased flexibility?

[dcaldastp]

Allow the client to access additional metadata when running the custom measureElement item callback.

For example, if I'm caching height values on the client side to avoid expensive recalculations on certain scenarios I could do ,this given access to the index of the measurable element through an extra metadata parameter.

const cacheHeights = new Map()
// ...
const rowVirtualizer = useVirtualizer({
  // ... 
  measureElement: (el, instance, metadata) => {
    if (cacheHeights.has(metadata.getItemKey(metadata.index))) {
      return cacheHeights.get(metadata.getItemKey(metadata.index));
    }
    const elHeight = el.getBoundingClientRect().height ?? estimateSize()
    return elHeight
  },
})

Thoughts on this? Other alternatives to achieve the same with the current APIs that I'm missing?

Thanks!