Upgrade node-mapnik and use a less restrictive version pinning (and release a new version)

[n-peugnet]

Please consider upgrading node-mapnik to at least 4.5 as it seems to use a lot more stable node extension API:

Starting from v4.5.0, node-mapnik module is published as "universal" binaries using node-addon-api All Node.js versions >= 10 are known to work, consult N-API documentation for more details: https://nodejs.org/dist/latest/docs/api/n-api.html#n_api_node_api_version_matrix

This will allow to use this package on current platforms easily. It tried to apply this simple patch and it allowed me to run npm install wich was completely failing previously because of my recent node version.

diff --git a/package.json b/package.json
index afd8ecb..3270132 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
   "dependencies": {
     "step": "~0.0.5",
     "generic-pool": "~2.4.0",
-    "mapnik": "~3.7.0",
+    "mapnik": "~4.5",
     "mime": "~1.3.4"
   },
   "devDependencies": {

I ran the test and all of them passed correctly, but I don't know how much of the library code is tested.

Tests results

$ npm run test

> @mapbox/[email protected] test
> mocha -R spec --timeout 10000



  Closing behavior 
    ✓ should close cleanly 1 (504ms)
    ✓ should close cleanly 2 (327ms)
    ✓ should throw with invalid usage (close before getTile) (301ms)
    ✓ should throw with invalid usage (close after getTile) (324ms)

  Handling Errors 
    ✓ invalid style (301ms)
    ✓ invalid font, strict (297ms)
    ✓ invalid font, non-strict (default) (296ms)
    ✓ missing data (295ms)
    ✓ bad style (292ms)
    ✓ invalid image format (311ms)
    ✓ invalid image format 2 (315ms)

  Render 
    getGrid() 
      ✓ validates (44ms)

  Grid Render Errors 
    ✓ invalid layer (304ms)

  Info 
    ✓ getInfo() (310ms)
    ✓ getInfo() with XML string (307ms)
    ✓ getInfo() with template (304ms)
    ✓ getInfo() with jpeg format defined (300ms)
    ✓ creates backend from string with correct internal boolean values 1
    ✓ creates backend from string with correct internal boolean values 2
    ✓ creates backend from object with correct internal boolean values

  locking cache
    ✓ cache works
    ✓ multiple requests get same response
    ✓ errors get propagated
    ✓ multiple error-ed requests get the same response
    ✓ derived keys get the same response
    ✓ .clear()
    ✓ .del()
    ✓ later requests get a cached response
    ✓ test cache with timeout=0

  metatile
    ✓ test metatile calculation at z=0
    ✓ test metatile calculation at z=1
    ✓ test metatile calculation at z=2

  Render 
    ✓ getTile() override format
    getTile() 
      ✓ validates (94ms)
    getTile() with XML string
      ✓ validates (92ms)

  .mapnik
    ✓ exposes the mapnik binding


  36 passing (6s)