Start to reorganize

Display/src/app/components/nav/nav.component.ts

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+import { Component } from '@angular/core';
+import { BreakpointObserver, Breakpoints } from '@angular/cdk/layout';
+import { Observable } from 'rxjs';
+import { map, shareReplay } from 'rxjs/operators';
+
+@Component({
+  selector: 'app-nav',
+  templateUrl: './nav.component.html',
+  styleUrls: ['./nav.component.scss']
+})
+export class NavComponent {
+
+  isHandset$: Observable<boolean> = this.breakpointObserver.observe(Breakpoints.Handset)
+    .pipe(
+      map(result => result.matches),
+      shareReplay()
+    );
+
+  constructor(private breakpointObserver: BreakpointObserver) {}
+
+}