style(nav): fix X icon visibility issue (#1092)

Author: OlegDev1

src/components/Nav.module.css

@@ -15,11 +15,14 @@
 
 .icon svg {
   height: 16px;
-  fill: white;
   transition: 0.3s all;
   margin-top: 6px;
 }
 
+:global(.dark) .icon svg {
+  fill: white;
+}
+
 .icon svg:hover {
   opacity: 0.5;
 }
@@ -153,6 +156,10 @@ a.legacyLink {
 }
 
 @media (min-width: 1040px) {
+  .icon svg {
+    fill: white;
+  }
+
   .mobileOnly {
     display: none;
   }