update typescript to 3.9.5

typings/types.d.ts

@@ -161,7 +161,7 @@ export declare type removedNodeMutation = {
 };
 export declare type addedNodeMutation = {
     parentId: number;
-    previousId: number | null;
+    previousId?: number | null;
     nextId: number | null;
     node: serializedNodeWithId;
 };
@@ -296,6 +296,7 @@ export declare enum ReplayerEvents {
     SkipStart = "skip-start",
     SkipEnd = "skip-end",
     MouseInteraction = "mouse-interaction",
-    EventCast = "event-cast"
+    EventCast = "event-cast",
+    CustomEvent = "custom-event"
 }
 export {};