Write a migration guide

Write a migration guide for developers upgrading from [Version A] to [Version B] of [Library or Framework]. Open with a summary of the most impactful breaking changes. For each breaking change provide: what the old API or behaviour was, what the new API or behaviour is, a find-and-replace or codemod command where the change can be automated, and any caveats or cases where manual intervention is required. List deprecated APIs with their suggested replacements. Close with a step-by-step upgrade checklist.