fixing WCAG issues in header and menu

src/app/@theme/components/header/header.component.html

@@ -3,7 +3,9 @@
     <a (click)="toggleSidebar()" href="#" class="sidebar-toggle" aria-label="Open menu">
       <nb-icon icon="menu-2-outline"></nb-icon>
     </a>
-    <a class="logo" href="#" (click)="navigateHome()">ngx-<span>admin Y</span></a>
+    <h1>
+      <a class="logo" href="#" (click)="navigateHome()">ngx-<span>admin</span></a>
+    </h1>
   </div>
   <nb-select [selected]="currentTheme" (selectedChange)="changeTheme($event)" status="primary">
     <nb-option *ngFor="let theme of themes" [value]="theme.value"> {{ theme.name }}</nb-option>

src/app/@theme/layouts/one-column/one-column.layout.ts

@@ -10,7 +10,9 @@ import { Component } from '@angular/core';
       </nb-layout-header>
 
       <nb-sidebar class="menu-sidebar" tag="menu-sidebar" responsive>
-        <ng-content select="nb-menu"></ng-content>
+        <nav>
+          <ng-content select="nb-menu"></ng-content>
+        </nav>
       </nb-sidebar>
 
       <nb-layout-column>