ESLint 8 compatibility

[sindresorhus]

https://eslint.org/docs/8.0.0/user-guide/migrating-to-8.0.0

• Ensure our rules correctly handles class fields and top-level await.
  • Example: Update rules to support ES2022 class fields eslint/eslint#14857
• Changes to AST: https://eslint.org/docs/8.0.0/user-guide/migrating-to-8.0.0#changes-to-shorthand-property-ast-format

[bmish]

Also this breaking change needs to be handled in two places: https://eslint.org/docs/8.0.0/user-guide/migrating-to-8.0.0#the-lib-entrypoint-has-been-removed

• const baseRule = require('eslint/lib/rules/no-warning-comments');
• import {Linter, SourceCodeFixer} from 'eslint/lib/linter/index.js';

[fisker]

I'll work on this.