message: fix(Navigation): items in drop down respect external links
  With this change, navigation items displayed by a `ts-navigation` component will properly handle external links by using hrefs for them rather than router links.
diff: class="c-navigation__hidden-item qa-navigation-secondary-item"
  [ngClass]="{'c-navigation__hidden-item--admin': item.alwaysHidden}"
  routerLink="{{ item.destination }}"
  - *ngIf="item.destination"
  + *ngIf="item.destination && !item.isExternal"
  + mat-menu-item
  + #hiddenLinkElement
  + >
  + {{ item.name }}
  + </a>
  +
  + <a
  + class="c-navigation__hidden-item qa-navigation-secondary-item"
  + [ngClass]="{'c-navigation__hidden-item--admin': item.alwaysHidden}"
  + href="{{ item.destination }}"
  + *ngIf="item.destination && item.isExternal"
  mat-menu-item
  #hiddenLinkElement
  >
  