I can put together a very simple UI (probably one that just produces GeoJSON for you to copy-and-paste, although an advanced one could help you construct a pull request) using https://github.com/Leaflet/Leaflet.Editable - demo here: https://leaflet.github.io/Leaflet.Editable/example/index.html
I can put together a very simple UI (probably one that just produces GeoJSON for you to copy-and-paste, although an advanced one could help you construct a pull request) using https://github.com/Leaflet/Leaflet.Editable - demo here: https://leaflet.github.io/Leaflet.Editable/example/index.html