ESM support

Hi there, I'm trying to use umap-js with [Vitest](https://vitest.dev/guide/), but I'm getting this error:

```
TypeError: Cannot use require() to import an ES Module.
 ❯ .../node_modules/.pnpm/umap-js@1.4.0/node_modules/umap-js/dist/umap.js?mf_vitest_no_cjs_esm_shim:8
```

Is ESM support planned for `umap-js`?