Import raster-terrain & modified source use offset

- raster-terrain-offset imports raster-terrain.yaml and modifies the
terrain source to offset the tiles by 1

Author: tallytalwar

scenes/raster-terrain-offset.yaml

@@ -1,33 +1,5 @@
-global:
-    sdk_api_key: ''
-    sdk_landcover_api_key: ''
+import: raster-terrain.yaml
 
 sources:
-  nextzen:
-    type: MVT
-    url: https://tile.nextzen.org/tilezen/vector/v1/256/all/{z}/{x}/{y}.mvt
-    url_params:
-        api_key: global.sdk_api_key
-    rasters: ['terrain']
-  terrain:
-    type: Raster
-    url: https://d3gy1yxv8mxm7h.cloudfront.net/tilezen/landcover/v1/512/all/{z}/{x}/{y}.png
-    url_params:
-        api_key: global.sdk_landcover_api_key
-    zoom_offset: 1
-
-styles:
-  raster-test:
-    base: raster
-    shaders:
-      blocks:
-        color: 
-          "color.rgba = sampleRasterAtPixel(0, vec2(currentRasterPixel(0)));"
-
-layers:
-  earth:
-    data: { source: nextzen }
-    draw:
-      raster-test:
-        order: 1
-        color: white
+    terrain-normals:
+        zoom_offset: 1