Convert project to TypeScript

Hey @porsager! I would like to try and help you out a bit. I would like to convert the project to primarily use TypeScript. With LTS Node.js versions now supporting TypeScript files (via [erasableSyntaxOnly](https://www.typescriptlang.org/tsconfig/#erasableSyntaxOnly)), using TypeScript is quite a bit simpler, easier and less hassle. I would like to start with bundling. I want to use [Rolldown](https://rolldown.rs/), Vite is already bundled with it https://github.com/vitejs/vite/pull/19925. Then I'll convert `src` one file at a time to TypeScript. I have some experience on [meilisearch-js](https://github.com/meilisearch/meilisearch-js/pulls?q=is%3Aclosed+is%3Apr+author%3Aflevi29+).