Add combo layer that shows the NOAA20 VIIRS layer (closes #2538)

data/assets/scene/solarsystem/planets/earth/default_layers.asset

@@ -1,6 +1,7 @@
 -- Color layers
 asset.require("./layers/colorlayers/blue_marble", false)
 asset.require("./layers/colorlayers/esri_viirs_combo", true)
+asset.require("./layers/colorlayers/esri_noaa20_combo", false)
 asset.require("./layers/colorlayers/esri_world_imagery", false)
 asset.require("./layers/colorlayers/viirs_snpp_temporal", false)
 asset.require("./layers/colorlayers/aqua_modis_temporal", false)

data/assets/scene/solarsystem/planets/earth/layers/colorlayers/esri_noaa20_combo.asset

@@ -0,0 +1,67 @@
+local globeIdentifier = asset.require("../../earth").Earth.Identifier
+
+local layer = {
+  Identifier = "ESRI_NOAA20_Combo",
+  Name = "ESRI NOAA20 Combo",
+  Enabled = asset.enabled,
+  Type = "ByLevelTileLayer",
+  LevelTileProviders = {
+    {
+      MaxLevel = 4,
+      TileProvider = {
+        Identifier = "Temporal_VIIRS_NOAA20",
+        Name = "Temporal VIIRS NOAA20",
+        Type = "TemporalTileLayer",
+        Mode = "Prototyped",
+        Prototyped = {
+          Time = {
+            Start = "2020-04-25",
+            End = "Today"
+          },
+          TemporalResolution = "1d",
+          TimeFormat = "YYYY-MM-DD",
+          Prototype = openspace.globebrowsing.createTemporalGibsGdalXml(
+            "VIIRS_NOAA20_CorrectedReflectance_TrueColor",
+            "250m",
+            "jpg"
+          )
+        },
+        PadTiles = false
+      }
+    },
+    {
+      MaxLevel = 22,
+      TileProvider = {
+        Identifier = "ESRI_World_Imagery",
+        Name = "ESRI World Imagery",
+        FilePath = asset.localResource("esri_world_imagery.wms"),
+        PadTiles = false
+      }
+    },
+  },
+  PadTiles = false,
+  Description = [[Level based layer combining "NOAA20 SNPP (Temporal)" and ESRI World
+    Imagery. "NOAA20 SNPP (Temporal)" is faded out at tile level 4]]
+}
+
+asset.onInitialize(function()
+  openspace.globebrowsing.addLayer(globeIdentifier, "ColorLayers", layer)
+end)
+
+asset.onDeinitialize(function()
+  openspace.globebrowsing.deleteLayer(globeIdentifier, "ColorLayers", layer)
+end)
+
+asset.export("layer", layer)
+
+
+
+asset.meta = {
+  Name = "ESRI NOAA20 VIIRS Combo",
+  Version = "1.0",
+  Description = [[Level based layer combining "NOAA20 SNPP (Temporal)" and ESRI World
+  Imagery. "NOAA20 SNPP (Temporal)" is faded out at tile level 4]],
+  Author = "OpenSpace Tem",
+  URL = "http://www.openspaceproject.com",
+  License = "MIT License"
+}