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/actions/types.ts

@@ -21,7 +21,7 @@ export interface Action {
   PanelComponent?: React.FC<{
     elements: readonly ExcalidrawElement[];
     appState: AppState;
-    updateData: (formData: any) => void;
+    updateData: (formData?: any) => void;
   }>;
   perform: ActionFn;
   keyPriority?: number;