Update mobile menu sticky button styles

src/components/navigation/menu/menu.scss

@@ -92,24 +92,28 @@
 }
 
 .hy-link__donate {
-  align-items: center;
-  background-color: var(--brand-main);
+  background-color: var(--grayscale-white);
   bottom: -20px;
-  display: flex;
-  justify-content: center;
-  letter-spacing: -0.5px;
-  margin: auto -20px 0;
-  padding: 20px;
   position: sticky;
   z-index: 102;
 
   a {
-    @include font-size(15px, 20px);
+    @include font-size(16px, 16px);
     @include font-weight($semibold);
+    background-color: var(--brand-main-light);
     color: var(--grayscale-white);
+    display: block;
     font-family: var(--main-font-family);
+    letter-spacing: -0.4px;
+    margin: 12px;
+    padding: 20px;
+    text-align: center;
     text-decoration: none;
 
+    @include breakpoint($narrow) {
+      margin: 12px 28px;
+    }
+
     &:focus {
       outline: solid 2px var(--additional-yellow);
       outline-offset: 4px;