Add info button to statistics-page

src/app/components/shared/statistics-page/statistics-page.component.html

@@ -2,6 +2,7 @@
   <mat-card>
     <mat-card-header>
       <h2>{{'statistic.learning-status' | translate}}</h2>
+      <h2 class="help"><mat-icon>help</mat-icon></h2>
     </mat-card-header>
     <mat-divider></mat-divider>
     <div *ngIf="isLoading"                                                                                                                                                                                                                                                                                                                                                          fxLayout="column" fxLayoutAlign="center" fxLayoutGap="20px" fxFill>