Reintroduce multi-point arrows and add migration for it (#635)

* Revert "Revert "Feature: Multi Point Arrows (#338)" (#634)"

This reverts commit 3d2e59bfed.

* Convert old arrow spec to new one

* Remove unnecessary failchecks and fix context transform issue in retina displays

* Remove old points failcheck from getArrowAbsoluteBounds

* Remove all failchecks for old arrow

* remove the rest of unnecessary checks

* Set default values for the arrow during import

* Add translations

* fix restore using unmigrated elements for state computation

* don't use width/height when migrating from new arrow spec

Co-authored-by: David Luzar <luzar.david@gmail.com>
Co-authored-by: Christopher Chedeau <vjeuxx@gmail.com>

src/appState.ts

@@ -7,6 +7,7 @@ export function getDefaultAppState(): AppState {
   return {
     draggingElement: null,
     resizingElement: null,
+    multiElement: null,
     editingElement: null,
     elementType: "selection",
     elementLocked: false,
@@ -26,3 +27,9 @@ export function getDefaultAppState(): AppState {
     name: DEFAULT_PROJECT_NAME,
   };
 }
+
+export function cleanAppStateForExport(appState: AppState) {
+  return {
+    viewBackgroundColor: appState.viewBackgroundColor,
+  };
+}