code: function addPoints(sourceName, n_points = 10) {
    for (let i = 0; i < n_points; i++) {
      // the feature is a normal GeoJSON feature definition
      store.dispatch(mapActions.addFeatures(sourceName, [{
        type: 'Feature',
        properties: {
          id: `point${i}`,
          title: 'Random Point',
        },
        geometry: {
          type: 'Point',
          // this generates a point somewhere on the planet, unbounded.
          coordinates: [(Math.random() * 360) - 180, (Math.random() * 180) - 90],
        },
      }]));
    }
  }
docs: Handy all around function for adding a random
  set of points to the map.
  @param {string} sourceName The name of the source to add to.
  @param {number} n_points Number of random points to add.