feat!: upgrade to ESLint v9

[dcroote]

Closes #108, supersedes #6, #9, and #98. This will require bumping ESLint for all consumers, but since v8 was end of life October 2024, it seems like it's time.

There is one warning on install:

 WARN  Issues with peer dependencies found
.
└─┬ @shopify/eslint-plugin 47.0.1
  └── ✕ unmet peer eslint@^8.56.0: found 9.20.1

However it seems like it's OK.

[Siegrift]

👍 LGTM

[dcroote]

Ugh this was too optimistic. All the src/ configs need to be converted too. It's a mess with stupid commonjs & esm conflicts everywhere. I'm converting this repo to typescript and will dual export commonjs & esm.