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/manager.tsx

@@ -83,7 +83,7 @@ export class ActionManager implements ActionsManagerInterface {
     if (this.actions[name] && "PanelComponent" in this.actions[name]) {
       const action = this.actions[name];
       const PanelComponent = action.PanelComponent!;
-      const updateData = (formState: any) => {
+      const updateData = (formState?: any) => {
         const commitToHistory =
           action.commitToHistory &&
           action.commitToHistory(this.getAppState(), this.getElements());