Require ESLint 8

[fisker]

• Use es2021: true instead of es6: true.
• Add tests to validate it actually works
• Drop support for ESLint v7

Can't use es2022

Error {
    message: `--config:
        Environment key "es2022" is unknown
    `,
  }

Actually, I was going to remove env, I thought setting ecmaVersion auto enables those envs, I'll investigate.

[fisker]

I was wrong about env, https://eslint.org/docs/user-guide/configuring/language-options#specifying-parser-options

For ES6 syntax, use { "parserOptions": { "ecmaVersion": 6 } }; for new ES6 global variables, use { "env": { "es6": true } }. { "env": { "es6": true } } enables ES6 syntax automatically, but { "parserOptions": { "ecmaVersion": 6 } } does not enable ES6 globals automatically.

[sindresorhus]

And since we're dropping ESLint 7:

eslint-plugin-unicorn/rules/utils/get-builtin-rule.js

Lines 4 to 5 in f14aa95

	// TODO: Remove this when we drop support for ESLint 7
	const eslintVersion = require('eslint/package.json').version;

[alfaproject]

I think you mean it requires eslint@8.9 because according to our CI the update to this version is not compatible with 8.8...

Can you tell me exactly why es2022 is needed? Seems like an unnecessary breaking change for no real reason

[fisker]

Sorry, this PR was created before ESLint release 8.9, add es2022 was added in that version.

no real reason

No reason, but we only want to support the latest version, if this cause problems, you can pin to v40.

[alfaproject]

No problems, we just updated to eslint 8.9 anyway but maybe worth to update the change log. More curiosity than anything