Use data-s9e-livepreview-hash to skip DOM diffing

[JoshyPHP]

When data-s9e-livepreview-hash is set, the live preview algorithm will use it as a hint to determine whether to skip that entire branch of the DOM. Extensions like MathRen replace plain text with markup, so every time any part of the message is refreshed the fancy KaTeX markup reverts to text, then the live preview algorithm reruns the data-s9e-livepreview-onupdate code to change it back to KaTeX then does DOM diffing to see if the live DOM needs to be updated. If you set data-s9e-livepreview-hash, it will make a hash of the element's markup before the update event is run so it will only run it if the content actually changes. IOW, it won't run katex.render() on every keystroke.

https://s9etextformatter.readthedocs.io/JavaScript/Live_preview_attributes/#data-s9e-livepreview-hash