Add 'Zoom with Scroll' input navigation scheme to preferences (#1021)

* Add use_scroll_as_zoom field to preference handler

* Add {Create,Delete}Mapping variants to message

* Revert "Add {Create,Delete}Mapping variants to message"

This reverts commit 0ba74754c9fb0c78d0b590c96e1d4fe2cfdd13e7.

* Revert "Add use_scroll_as_zoom field to preference handler"

This reverts commit d30f7c9edfa6d6e156939ca07f4db81f288975fd.

* Add basic scroll_as_zoom mapping

* Create overengineered mapping patch abstraction

* Add (for now passthrough) input layout manager

* Actually handle ModifyLayout messages (untested)

* Add backend preferences <-> layout manager comms

* Add scroll-as-zoom to actual preferences UI

* Rename LayoutManager -> KeyMapping

* Add Input section to preferences and title case

* Add scrollAsZoom frontend handling code (untested)

* Handle frontend <-> preferences comms

* (broken) Move scrollAsZoom persistence into state

* Fix scrollAsZoom having no effect on node graph

* Remove debugging helpers

* Fix confusion between horizontal and vertical

* Rename feature

* Move new message handler into folder

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/messages/frontend/frontend_message.rs

@@ -266,4 +266,8 @@ pub enum FrontendMessage {
 		layout_target: LayoutTarget,
 		diff: Vec<WidgetDiff>,
 	},
+	UpdateZoomWithScroll {
+		#[serde(rename = "zoomWithScroll")]
+		zoom_with_scroll: bool,
+	},
 }