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/element/index.ts

@@ -23,3 +23,4 @@ export {
   resizePerfectLineForNWHandler,
   normalizeDimensions,
 } from "./sizeHelpers";
+export { showSelectedShapeActions } from "./showSelectedShapeActions";