build (and tweak) annotations baseline image

Author: alexcjohnson

test/image/baselines/annotations.png

@@ -46,11 +46,11 @@
             {"text":"","showarrow":true,"borderwidth":1.2,"arrowhead":2,"axref":"x","ayref":"y","x":5,"y":3,"ax":4,"ay":5},
             {"text":"","showarrow":true,"borderwidth":1.2,"arrowhead":2,"axref":"x","ayref":"y","x":6,"y":2,"ax":3,"ay":3},
             {
-                "text": "arrow BL<br>+standoff", "x": 2, "y": 2, "ax": 20, "ay": 20,
-                "xanchor": "left", "yanchor": "bottom", "standoff": 5
+                "text": "arrow ML<br>+standoff", "x": 2, "y": 2, "ax": 20, "ay": 20,
+                "xanchor": "left", "yanchor": "middle", "standoff": 5
             },
             {
-                "text": "angle, arrow TM<br>box+standoff", "x": 2, "y": 2, "ax": -20, "ay": -20,
+                "text": "angle, arrow TR<br>box+standoff", "x": 2, "y": 2, "ax": -20, "ay": -20,
                 "xanchor": "right", "yanchor": "top", "standoff": 5, "textangle": 45, "bordercolor": "#444"
             }
         ]