refactor project to use JSON Modules

After the upgrade to #1014 for Node v18 support, we can now refactor all instances of reading a JSON file to use native JSON modules, using import assertions

// before
const packageJson = JSON.parse(fs.readFileSync('./package.json', 'utf-8'));
const greenwoodPackageJson = JSON.parse(await fs.promises.readFile(new URL('../package.json', import.meta.url), 'utf-8'))

// after
import packageConfig from './package.json' assert { type: 'json' };

So goal would be to go and replace all those instances to the new version.

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This will also require us updating our ESLint version to include support for import assertions, which we might still need to wait for? https://github.com/eslint/eslint/discussions/15305

Or maybe we can get around it with a plugin?

• https://github.com/eslint/eslint/discussions/15305#discussioncomment-2508948
• https://stackoverflow.com/questions/71090960/is-there-a-way-to-make-eslint-understand-the-new-import-assertion-syntax-without