build: switch from yarn to npm to manage js dependencies and move js contents to root

yarn v1 is being deprecated and starts to have some issues

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

src/types/followedGroupEvent.model.ts

@@ -0,0 +1,10 @@
+import { IEvent } from "./event.model";
+import { IPerson, IGroup } from "./actor";
+import { IUser } from "./current-user.model";
+
+export interface IFollowedGroupEvent {
+  profile: IPerson;
+  group: IGroup;
+  user: IUser;
+  event: IEvent;
+}