React18 String Refs

If you're migrating a React codebase to 18.3.1 or 19 and hitting string ref warnings, this gives you the exact patterns to convert ref="name" and this.refs.name to React.createRef(). It covers the straightforward cases like single element refs, but the real value is in the tricky scenarios like refs in lists where you need different approaches than just search and replace. Includes grep commands to scan your codebase for both halves of the pattern, which is helpful since string refs have two locations that need changing. Honestly a narrow use case, but if you're doing this migration on any moderately sized codebase, having the patterns written out prevents the kind of mistakes that waste an afternoon.