Migrate library from CJS to ESM #640
Description
Migrate the library module system from CommonJS to ECMAScript Modules (ESM).
ESM is the official JavaScript module system and enables bundlers to tree-shake unused code, resulting in smaller bundles for library consumers. It also provides better static analysis, improved IDE and TypeScript support, and access to modern features like top-level await. The broader ecosystem has largely moved to ESM, and Node.js 22+ now supports require() of ESM modules, making this the right time to migrate.