feature: scrollbar on left-menu and content added

src/styles/content/_index.scss

@@ -96,4 +96,64 @@ main {
       }
     }
   }
-}
+}
+
+/* Add scrollbar to the left and to the content */
+.scrollbar-nav,
+.scrollbar-content {
+  overflow-y: auto;
+  height: calc(100vh - 72px); /* 72px == header's height */
+  -webkit-overflow-scrolling: touch;
+  -ms-overflow-style: none;
+}
+
+/* Custom scrollbar of the left-menu*/
+/* Works on Firefox*/
+.scrollbar-nav {
+  scrollbar-width: thin;
+  scrollbar-color:#D6CECE var(--color-heading);
+}
+
+/* Works on Chrome, Edge, and Safari */
+.scrollbar-nav {
+  &::-webkit-scrollbar {
+    width: 12px;
+  }
+
+  &::-webkit-scrollbar-track {
+    background: var(--color-heading);          /* color of the tracking area */
+  }
+
+  &::-webkit-scrollbar-thumb {
+    background-color:#D6CECE;                /* color of the scroll thumb */
+    border-radius: 6px;                        /* roundness of the scroll thumb */
+    border: 3px solid var(--color-heading);    /* creates padding around scroll thumb */
+  }
+}
+
+
+
+
+/* Custom scrollbar of the content */
+/* Works on Firefox */
+.scrollbar-content {
+  scrollbar-width: thin;
+  scrollbar-color:#D6CECE white;            /* scroll thumb and track */
+}
+
+/* Works on Chrome, Edge, and Safari */
+.scrollbar-content {
+  &::-webkit-scrollbar {
+    width: 12px;
+  }
+
+  &::-webkit-scrollbar-track {
+    background: white;                        /* color of the tracking area */
+  }
+
+  &::-webkit-scrollbar-thumb {
+    background-color:#D6CECE;                 /* color of the scroll thumb */
+    border-radius: 6px;                         /* roundness of the scroll thumb */
+    border: 3px solid white;                  /* creates padding around scroll thumb */
+  }
+}