// breakpoint observer checks if width is over 700px.
// If so use 'over' mode and close side nav
// If less than 700px use 'side' mode & open side nav
ngAfterViewInit() {
  this.observer
    .observe(["(max-width: 700px)"])
    .pipe(delay(1)) // delay 1mS
    .subscribe((res) => {
      if (res.matches) {
        this.sidenav.mode = "over";
        this.sidenav.close();
      } else {
        this.sidenav.mode = "side";
        this.sidenav.open();
      }
    });
}