Update side menu header.

frontend/src/app/components/header/header.component.scss

@@ -33,6 +33,9 @@ $headerHeight: 3.5em;
                 display: flex;
                 justify-content: center;
                 align-items: center;
+                $buttonSize: 2.5em;
+                width: $buttonSize;
+                height: $buttonSize;
 
                 &:hover {
                     cursor: pointer;