fix: fix CSS issues

- top mobile banner margin & border radius was incorrect
- fix spacing issue in footer links

scss/_off.scss

@@ -1283,6 +1283,12 @@ $section-cyan: #008c8c;
   }
 }
 
+// Top banner to download mobile app
+#mobile-app-top-banner {
+  margin: 0;
+  border-radius: 0;
+}
+
 .footer_social_icon {
   height: 24px;
   vertical-align: middle;
@@ -1463,6 +1469,17 @@ $section-cyan: #008c8c;
 }
 
 
+// Contribute and discover footer
+
+#contribute_and_discover_links_block {
+  padding-left: 1rem;
+  padding-right: 1rem;
+
+  p {
+    margin-bottom: 0.5rem;
+  }
+}
+
 // Title with Plus Jakarta Sans, according to brand guidelines
 .emphasized-title {
   font-family: "Plus Jakarta Sans", $font-family-sans-serif;