OZG-7047 Add tooltip to a11y button

alfa-client/libs/common/src/lib/accessibility-button/accessibility-button.component.ts

 import { CommonModule } from '@angular/common';
 import { Component, Input } from '@angular/core';
-import { AccessibilityIconComponent, LinkComponent } from '@ods/system';
+import { AccessibilityIconComponent, LinkComponent, TooltipDirective } from '@ods/system';
 
 @Component({
   selector: 'common-accessibility-button',
   standalone: true,
-  imports: [CommonModule, AccessibilityIconComponent, LinkComponent],
-  template: `<ods-link [url]="url" [linkTestId]="linkTestId"><ods-accessibility-icon size="large" /></ods-link>`,
+  imports: [CommonModule, AccessibilityIconComponent, LinkComponent, TooltipDirective],
+  template: `<ods-link [url]="url" [linkTestId]="linkTestId" tooltip="Barrierefreiheit"
+    ><ods-accessibility-icon size="large"
+  /></ods-link>`,
 })
 export class AccessibilityButtonComponent {
   @Input({ required: true }) url!: string;