Centered header-title

src/app/components/shared/header/header.component.html

@@ -3,6 +3,7 @@
     <button *ngIf="router.url !== '/home'" (click)="goBack()" mat-icon-button>
       <mat-icon aria-label="Go back">keyboard_arrow_left</mat-icon>
     </button>
+    <span class="fill-remaining-space"></span>
     <span class="app-title" (click)="goToHomepage()">ARSnova</span>
     <span class="fill-remaining-space"></span>
 

src/app/components/shared/header/header.component.scss

 .app-title {
   cursor: pointer;
+  margin: 0 auto;
 }