Add custom hamburger menu icon and remove unused vars

resources/assets/styles/common/_variables.scss

@@ -32,14 +32,11 @@ $btn-transition: color 0.6s ease;
 // Modal
 $modal-content-border-radius: 0;
 
-/** Hamburger icon */
-$hamburger-padding-x: 0;
-$hamburger-padding-y: 0;
-$hamburger-layer-width: 25px;
-$hamburger-layer-height: 3px;
-$hamburger-layer-spacing: 4px;
-$hamburger-layer-color: #182340;
-$hamburger-types: (vortex);
+// Hamburger icon
+$navbar-dark-toggler-icon-bg: "url('data:image/svg+xml,%3Csvg aria-hidden='true' data-prefix='fas' data-icon='bars' class='svg-inline--fa fa-bars fa-w-14' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='#ffffff' d='M16 132h416c8.837 0 16-7.163 16-16V76c0-8.837-7.163-16-16-16H16C7.163 60 0 67.163 0 76v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16z'/%3E%3C/svg%3E')";
+$navbar-light-toggler-icon-bg: "url('data:image/svg+xml,%3Csvg aria-hidden='true' data-prefix='fas' data-icon='bars' class='svg-inline--fa fa-bars fa-w-14' xmlns='http://www.w3.org/2000/svg' viewBox='0 0 448 512'%3E%3Cpath fill='#00000080' d='M16 132h416c8.837 0 16-7.163 16-16V76c0-8.837-7.163-16-16-16H16C7.163 60 0 67.163 0 76v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16z'/%3E%3C/svg%3E')";
+$navbar-dark-toggler-border-color: "none";
+$navbar-light-toggler-border-color: "none";
 
 body {
   font-family: $font-sans !important;