Canvas zooming (#716)

* Zoom icons.

* Actions.

* Min zoom of 0 does not make sense.

* Zoom logic.

* Modify how zoom affects selection rendering.

* More precise scrollbar dimensions.

* Adjust elements visibility and scrollbars.

* Normalized canvas width and height.

* Apply zoom to resize test.

* [WIP] Zoom using canvas center as an origin.

* Undo zoom on `getScrollBars`.

* WIP: center zoom origin via scroll

* This was wrong for sure.

* Finish scaling using center as origin.

* Almost there.

* Scroll offset should be not part of zoom transforms.

* Better naming.

* Wheel movement should be the same no matter the zoom level.

* Panning movement should be the same no matter the zoom level.

* Fix elements pasting.

* Fix text WYSIWGT.

* Fix scrollbars and visibility.

src/appState.ts

@@ -28,6 +28,7 @@ export function getDefaultAppState(): AppState {
     name: DEFAULT_PROJECT_NAME,
     isResizing: false,
     selectionElement: null,
+    zoom: 1,
   };
 }