[custom map suggestion] Add the ability to use arbitrary mapbox styles as custom layers

[pfbreton-perso]

I noticed that Mapbox styles are used for some of the layers now. I developed my own Mapbox styles and by hacking around I managed to override locally one of the map style which demonstrated that by passing around the correct URL it works here is an image showing my local hack where I redirected the Mapbox Outdoors styl to my own.

Since we can alreay create our own layers which uses a WMTS protocol (XYZ tiles) it seems that we could also allow for custom mapboxstyles & tokenns.

[vcoppe]

Thank you for your suggestion, I have re-implemented the website from scratch and you can now add custom vector layers.
For now this is done by giving the URL of the Mapbox style JSON, let me know if you had something else in mind.
You can check out the future website here: https://gpx.studio/gpx.studio/ and provide feedback on this new repository: https://github.com/gpxstudio/gpx.studio.