fix(eslint-plugin-next): ensure named exports for ESM compatibility

[rajnish93]

What?

Refactored the exports in packages/eslint-plugin-next/src/index.ts to explicitly assign named exports (configs, rules, meta) to module.exports in a way that is statically analyzable by Node.js's CJS-ESM interop (specifically cjs-module-lexer).

Why?

Fixes #86504

When importing @next/eslint-plugin-next in an ESM environment (like eslint.config.js or using node -e "import ..."), named imports such as import { configs } from '@next/eslint-plugin-next' were failing.

This happened because swc compiles the previous export const syntax into Object.defineProperty getters. While valid CommonJS, Node.js's cjs-module-lexer cannot detect these dynamic getters as named exports, leading to a runtime error: SyntaxError: Named export 'configs' not found.

How?

I updated the entry point (src/index.ts) to:

1. Directly assign module.exports = plugin for the default export.
2. Explicitly assign exports.configs, exports.rules, and exports.meta as properties.

This pattern ensures that:

• CommonJS consumers (using require) receive the expected plugin object with properties.
• ESM consumers (using import) can successfully import named exports because cjs-module-lexer can now detect the exports.prop = ... pattern.

Verified the fix using the reproduction script from the issue:
node -e "import {configs} from '@next/eslint-plugin-next'; console.log(Object.keys(configs))"

Output: [ 'recommended-legacy', 'core-web-vitals-legacy', 'recommended', 'core-web-vitals' ]Fixes #86504

[ijjk]

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