Mapbox vector layer

[tschaub]

This adds a MapboxVector layer constructor that can be used to render a Mapbox-hosted style. As mentioned in the docs, this only works with vector type sources. For styles that have more than a single source, the layer can be configured with a source property to indicate the id of the source to use. The layers property can also be used to render a subset of layers in the style (provided that they share the same vector source).

Example usage:

new Map({
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2
  }),
  layers: [
    new MapboxVector({
      styleURL: 'mapbox://styles/tschaub/cjh953yhw1...',
      accessToken:'pk.redacted'
    })
  ]
});

Where the styleURL and accessToken are copied from studio:

See openlayers/ol-mapbox-style#268 for the original PR (and credits to that library for making this easy).

[ahocevar]

Wow, very impressive work @tschaub. And extra bonus points for the improvements to the rendering test and api doc systems you made along the way. Thanks!