dryrun: adds "migrate-i18next" script

[ahrjarrett]

Do not merge -- this is a dry-run

This PR tests the behavior of the i18next-selector-codemod.

Original ask: i18next/i18next#2322 (comment)

I included a demo of the codemod being used on electricitymaps-contrib in the package's README, which I'll share here too:

Todos

• Check: each call site to make sure the transformation is reasonable, doesn't contain any obvious bugs
• Fix: bug where [options object pointers aren't preserved](this line)
  • Fixed in feat(codemod): adds support for the options object being a pointer ahrjarrett/i18next-selector#5
  • Update this PR with the fix when complete
• Fix: bug where string key ternary expressions aren't transformed
  • Examples:
    • https://github.com/electricitymaps/electricitymaps-contrib/blob/master/web/src/components/buttons/LinkedinButton.tsx#L38
    • https://github.com/electricitymaps/electricitymaps-contrib/blob/master/web/src/components/buttons/RedditButton.tsx#L35
    • https://github.com/electricitymaps/electricitymaps-contrib/blob/master/web/src/components/buttons/TwitterButton.tsx#L34
  • Update this PR with the fix when complete

I've added these todos to our todo list, will push another commit + an update here when they're fixed