Chore: ng lint using the recommended @angular-eslint style

bookie/src/app/nav-bar/nav-bar.component.html

@@ -4,7 +4,7 @@
     Point of Sale
   </a>
   <span class="fill-remaining-space"></span>
-  <button mat-button [routerLink]="['/', 'login']" *ngIf="!(auth.currentUser | async)">
+  <button mat-button [routerLink]="['/', 'login']" *ngIf="(auth.currentUser | async) === null">
     <mat-icon>account_box</mat-icon>
     Login
   </button>