Option to switch to remote version of Mapbox GL JS v2

[walkerke]

Hi @crazycapivara -

Following our discussion in #103, this PR gives users the option to switch to a remote version of Mapbox GL JS v2. (An option to download the dependencies locally can follow, but I wanted to keep this minimal). The new function is mapboxer_use_v2(), which functions similarly to sf::sf_use_s2() in that users can supply TRUE or FALSE to switch the option on or off. The new code shouldn't impact any users' existing code, but gives users the option to incorporate new features in GL JS v2 if they want to switch on the option.

This example illustrates how to use the example in vector-layer-filled-polygons.R but with a 3D globe projection, available in GL JS v2.

library(mapboxer)
mapboxer_use_v2(TRUE)

vector_src <- mapbox_source(
  type = "vector",
  url = "mapbox://mapbox.country-boundaries-v1"
)

SRC_ID <- "country-boundaries-data"

layer_style <- list(
  "id" = "country-boundaries",
  "type" = "fill",
  "source" = SRC_ID,
  "source-layer" = "country_boundaries",
  "paint" = list(
    "fill-color" = "blue",
    "fill-opacity" = 0.6
  )
)

mapboxer(
  style = basemaps$Carto$positron,
  center = c(0, 0),
  zoom = 1, 
  projection = "globe"
) %>%
  add_source(vector_src, id = SRC_ID) %>%
  add_layer(layer_style)

Thanks for considering the PR!

[crazycapivara]

Hi @walkerke,
I'll check it as soon as poosible.

[srgorelik]

This works great! Exactly what I needed to render a globe in R Shiny. Thanks so much @crazycapivara for this package and @walkerke for your PR! 👏