Undo/Redo buttons, refactor menu toggles (#793)

* Make Undo & Redo and the menu buttons into actions; add undo/redo buttons

* Create variables for the ToolIcon colors

* Darken the menu buttons when they’re active

* Put the more intensive test in `perform`

* Fix & restyle hint viewer

* Add pinch zoom for macOS Safari

* Chrome/Firefox trackpad pinch zoom

* openedMenu → openMenu

* needsShapeEditor.ts → showSelectedShapeActions.ts

* Call showSelectedShapeActions

src/components/HintViewer.tsx

@@ -52,5 +52,9 @@ export const HintViewer = ({
     return null;
   }
 
-  return <div className="HintViewer">{hint}</div>;
+  return (
+    <div className="HintViewer">
+      <span>{hint}</span>
+    </div>
+  );
 };