Migrate away from CRA / fix React 18 createRoot deprecation warning

[jadeglaze]

react-dom.development.js:86 Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot

[mb21]

That's due to CRA (create-react-app aka react-scripts) being deprecated, see https://react.dev/blog/2025/02/14/sunsetting-create-react-app.

But I haven't evaluated what to move to. For PanWriter, we really don't need server-side-rendering, much of a router or anything like that (so Next and react router are out). Perhaps one of those? https://react.dev/learn/creating-a-react-app#other-frameworks

Then again, for the moment I'm also just fine sticking to React 17/18. For this app where we don't have a server, I'm not all that interested in the fast pace and the direction current React is being developed. Personally, I would be even up to switch to Solid (which is what we're using at work), but the migration is a lot of work with relatively little gain for this app.