Update to supported ESLint v9.x

[MikeMcC399]

What would you like?

Update the ESLint ecosystem used by npm repos to ESLint v9.x with current (flat) configuration files, migrating up from its current ESLint v8.x level using deprecated (eslintrc) configuration files.

Why is this needed?

The ESLint v8.x release line entered end-of-life on Oct 5, 2024. The current release line is v9.x.

npm should use a supported version of ESLint so that it can confidently lint into the future.

Other

This also involves @npmcli/eslint-config, which currently defines:

  "peerDependencies": {
    "eslint": "^8.13.0",
    "eslint-plugin-import": "^2.26.0",
    "eslint-plugin-node": "^11.1.0",
    "eslint-plugin-promise": "^6.0.0"
  }

Module	Configured	Latest	ESLint v9 flat compatible
eslint	^8.13.0	9.32.0	YES
eslint-plugin-import	^2.26.0	2.32.0	YES
eslint-plugin-node	^11.1.0	11.1.0	NO
eslint-plugin-promise	^6.0.0	7.2.1	YES

• eslint-plugin-node advises that it is no longer maintained, and recommends instead eslint-plugin-n

• See also Remove eslint-plugin-import #456