feat: support ESLint flat config

[bmish]

Added a new plugin export for using the flat config:

// eslint.config.js
const eslintPluginQunitRecommended = require("eslint-plugin-qunit/configs/recommended");

module.exports = [
    eslintPluginQunitRecommended,
];

Using legacy config is unchanged:

// .eslintrc.js
module.exports = {
  extends: ['plugin:qunit/recommended']
};

Prior art:

• feat: support eslint.config.js eslint-community/eslint-plugin-n#95
• feat: support eslint.config.js eslint-community/eslint-plugin-eslint-plugin#347
• https://eslint.org/docs/latest/use/configure/migration-guide

Follow-up to:

• chore: convert to eslint flat config internally #440

[coveralls]

coverage: 100.0%. remained the same
when pulling 51cd143 on bmish:support-eslint-flat-config
into bc854b0 on platinumazure:master.

[platinumazure]

Thanks for this, looks good. Sorry for the delay in reviewing.

I'm basically ready to merge this in, but I'd feel better if we could solve the Coveralls CI problem first (see #461) so that hopefully we don't get a Coveralls error on post-merge CI.

[Turbo87]

this update appears to fail for the crates.io project with:

ESLint: 8.56.0

Error: ESLint configuration in .eslintrc.js » plugin:qunit/recommended is invalid:
	- Unexpected top-level property "description".

see rust-lang/crates.io#8104

[bmish]

@Turbo87 fixing here:

• fix: remove disallowed description property from config #476