[openstreetmap/openstreetmap-website] Replace vendored leaflet.polyline plugin with @mapbox/polyline (PR #6996)

[Frank Elsinga]

### Description

We currently depend on the vendored leaflet dependency.
The regular npm dependency does the same thing

### How has this been tested?

<img width="3839" height="1817" alt="Screenshot_20260412_061814" src="https://github.com/user-attachments/assets/8f8b6ced-4a46-45b5-ab26-2a57a1a326cb" />

You can view, comment on, or merge this pull request online at:

  https://github.com/openstreetmap/openstreetmap-website/pull/6996

-- Commit Summary --

  * Replace vendored leaflet.polyline plugin with @mapbox/polyline

-- File Changes --

    M Vendorfile (4)
    M app/assets/javascripts/index.js (2)
    M app/assets/javascripts/index/directions/fossgis_osrm.js (2)
    M app/assets/javascripts/index/directions/fossgis_valhalla.js (2)
    M app/assets/javascripts/index/directions/graphhopper.js (2)
    A app/assets/javascripts/polyline_decoder.js (6)
    M package.json (1)
    A test/javascripts/polyline_decoder_test.js (21)
    D vendor/assets/leaflet/leaflet.polyline.js (233)
    M yarn.lock (365)

-- Patch Links --

https://github.com/openstreetmap/openstreetmap-website/pull/6996.patchhttps://github.com/openstreetmap/openstreetmap-website/pull/6996.diff
-- 
Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/openstreetmap-website/pull/6996
You are receiving this because you are subscribed to this thread.

Message ID: <openstreetmap/openstreetmap-website/pull/6996 at github.com>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/rails-dev/attachments/20260411/1f8baa68/attachment.htm>