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/index.ts

@@ -36,3 +36,4 @@ export {
 } from "./actionExport";
 
 export { actionCopyStyles, actionPasteStyles } from "./actionStyles";
+export { actionToggleCanvasMenu, actionToggleEditMenu } from "./actionMenu";