Check ylem performance in profiler tab of React dev tools

Just as a precaution, to weed out people dismissing ylem before giving it a fair shot, we should check out how ylem performs in the [react-dev-tools](https://chrome.google.com/webstore/detail/react-developer-tools/fmkadmapgofadopljbjfkapdkoienihi) **profiler** tab.

Specifically we should look for long render times or more likely high render call or DOM commit counts. (higher than expected I mean)

Start by running ylem with React Developer Tools open to the Profiler tab. Record render times, render-call counts, and DOM commit counts, then compare them with expected behavior or a suitable baseline. Done means the performance findings are documented and any unexpectedly high measurements are clearly identified.

Written by the indexing model from the issue text.