Fix IndexSizeError

✅ Solution

The "IndexSizeError" in netlify-cms often arises when attempting to select or manipulate text ranges within editor fields, especially after content updates that change the underlying document structure. This frequently happens with custom widgets or complex markdown structures. To fix it, ensure your custom widgets and any code manipulating editor selections correctly handle content changes by validating the offsets and node positions before attempting to `setStart`, `setEnd`, or similar range methods. Sanitize or normalize the selection range based on the actual DOM structure after content modifications to avoid out-of-bounds errors.