Add router link to the startpage in the navbar

src/styles/common.css

@@ -23,4 +23,12 @@ body {
     min-height: 100vh;
     display: flex;
     flex-direction: column;
+}
+
+.link {
+    text-decoration: none;
+}
+
+.link:hover:not(.button-link) {
+    text-decoration: underline;
 }