Add Snapping Options to the Snap Dropdown Menu (#1321)

* [wip]feat: add snapping options

* [wip]fix: use svelte component for optionsWidget

* fix: use apt PopoverButton types

* refactor: minor formatting improvements

* Fix popover layout

* [wip]feat: attempt implementing CheckboxInputData struct

* fix: use correct Checkbox struct 's default method

* fix: revert adding CheckboxInputData struct

- This reverts commit 2a481887fc.

* feat: use checkboxes for snapping options

* feat: add label to dropdown checkbox elements

* fix: separate Snap dropdown menu elements
- move each element into separate row

* [wip]feat: modularize snapping states
- maintain individual snapping states for document

* fix: snapping checkboxes' behavior
- checkboxes now update internal snapping state

* refactor: update snap states individually
- this prevents out-of-sync states
- enables reusing existing snap state object

* feat: snap to boxes and nodes conditionally

* [wip]feat: attempt to invert checkbox on update
- attempt implementing mutable WidgetCallback struct
- attempt using above struct to invert checkbox state on update

* Fix widget diffing

* refactor: remove unused code

* feat: align checkboxes consistently with labels

* feat: use separators to stylize snapping menu
- removes need for custom CSS and label property
- ensures consistency across the application

* refactor: remove unneeded css

---------

Co-authored-by: hypercube <0hypercube@gmail.com>, TrueDoctor <dennis@kobert.dev>

editor/src/messages/layout/layout_message_handler.rs

@@ -31,6 +31,10 @@ impl LayoutMessageHandler {
 							widget_path.push(index);
 							return Some((widget, widget_path));
 						}
+
+						if let Widget::PopoverButton(popover) = &widget.widget {
+							stack.extend(popover.options_widget.iter().enumerate().map(|(child, val)| ([widget_path.as_slice(), &[index, child]].concat(), val)));
+						}
 					}
 				}
 				// A section contains more LayoutGroups which we add to the stack.