ENH: Vertical flip for toggle icon (#39)

Author: choldgraf

sphinx_togglebutton/_static/togglebutton.css

@@ -64,15 +64,24 @@ button.toggle-button {
     stroke: currentColor;  /* So that we inherit the color of other text */
 }
 
+/* Rotate icon with admonitions so that it points down */
+.admonition.toggle .tb-icon {
+    transform: rotate(-90deg);
+}
+
+/* When the admonition is hidden, icon should flip upwards but retain rotation */
+/* We scaleX, in order to flip along Y, because it is rotated */
+.admonition.toggle .toggle-button-hidden .tb-icon {
+    transform: rotate(-90deg) scaleX(-1);
+}
+
+/* With details toggles, we don't rotate the icon so it points right */
 details.toggle-details .tb-icon {
     height: 1.4em;
     width: 1.4em;
     margin-top: 0.1em;  /* To center the button vertically */
 }
 
-.toggle-button-hidden .tb-icon {
-    transform: rotate(90deg);
-}
 
 /**
  * Details-based toggles.