[FIX] router: properly react on hashchange

Before this commit, hashchanges were not taken into account by the
router, if used in history mode.

Also, it's stupid, but i ran prettier on the codebase

src/core/observer.ts

@@ -25,7 +25,6 @@ export class Observer {
 
   notifyCB() {}
   async notifyChange() {
-
     this.dirty = true;
     await Promise.resolve();
     if (this.dirty) {