resolves #1698 - add geo_across-antimeridian mock

- while #1698 was fixed by the improve geo defaults,
  this 🔒 it down.

Author: etpinard

test/image/baselines/geo_across-antimeridian.png

@@ -0,0 +1,89 @@
+{
+    "data": [
+        {
+            "type": "scattergeo",
+            "lon": [170, 180, -180, -170],
+            "lat": [-50, -45, -10, -20.5],
+            "marker": { "size": 20 }
+        },
+        {
+            "type": "choropleth",
+            "locations": ["NZL", "AUS"],
+            "z": [0, 1],
+            "showscale": false
+        },
+        {
+            "type": "scattergeo",
+            "lon": [170, 180, -180, -170],
+            "lat": [-50, -45, -10, -20.5],
+            "marker": { "size": 20 },
+            "geo": "geo2"
+        },
+        {
+            "type": "choropleth",
+            "locations": ["NZL", "AUS"],
+            "z": [0, 1],
+            "showscale": false,
+            "geo": "geo2"
+        }
+    ],
+    "layout": {
+        "geo": {
+            "domain": {
+                "x": [0, 0.5],
+                "y": [0, 1]
+            },
+            "type": "miller",
+            "showocean": true,
+            "lonaxis": {
+                "showgrid": true,
+                "dtick": 2,
+                "range": [120, -120]
+            },
+            "projection": {
+                "scale": 2
+            },
+            "center": {
+                "lat": -45
+            }
+        },
+        "geo2": {
+            "domain": {
+                "x": [0.5, 1],
+                "y": [0, 1]
+            },
+            "type": "miller",
+            "showocean": true,
+            "lonaxis": {
+                "showgrid": true,
+                "dtick": 2,
+                "range": [150, -150]
+            },
+            "lataxis": {
+                "range": [-90, 0]
+            }
+        },
+        "annotations": [{
+            "showarrow": false,
+            "xref": "paper",
+            "yref": "paper",
+            "x": 0.25,
+            "y": 1,
+            "xanchor": "center",
+            "yanchor": "bottom",
+            "text": "set <i>lonaxis.range</i>, <i>center.lon</i> and <i>projection.scale</i>"
+        }, {
+            "showarrow": false,
+            "xref": "paper",
+            "yref": "paper",
+            "x": 0.75,
+            "y": 1,
+            "xanchor": "center",
+            "yanchor": "bottom",
+            "text": "set <i>lonaxis.range</i> and <i>lataxis.range</i>"
+        }],
+        "showlegend": false,
+        "width": 700,
+        "height": 440
+    }
+}