The `node16` module resolution requires imports to use the `.js` file
extension in type definitions.
`@rollup/plugin-typescript` is needed to make this work with the Vite
setup used by Mermaid.
The module option for Mermaid internally is set to `nodenext`. This is
needed to support `.json` imports. Note that setting `module` to
`node16` or `nodenext` implies a matching `moduleResolution` value.
