Publish osm2lanes NPM package

For @kfarr to try out in 3dstreet. Should be a JS API with OSM tags as input (just a string/string map) and JSON lane specifications (something like `[{lane_type: "driving", width: 2.5, direction: "forward"}, ...]`) as output.

- [x] Create osm2lanes-js and publish to NPM
- [ ] Clean up the hasty refactor, possibly having a crate in the osm2streets repo with base types
- [ ] Stop re-exporting types from osm2streets crate?

Look at the existing osm2lanes-js package structure and its connection to the osm2streets Rust crate. Understand the base types that need to be shared and the API design for converting OSM tags to lane specifications. Check for any existing refactoring work and decide on the separation of types between the JS and Rust crates.

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