Fix layout scrolling when navigation bar is to tall

resources/style/index.css

@@ -3,11 +3,19 @@ body {
     flex-direction: row;
 }
 
+#navigation {
+    display: flex;
+    flex-direction: column;
+    height: 100%;
+}
+
 #service-selector {
     flex-grow: 1;
     display: block;
     margin: 0;
     padding: 0;
+
+    overflow-y: auto;
 }
 
 #service-selector [draggable] {

resources/style/layout.css

@@ -78,3 +78,21 @@ button:hover {
 .hidden {
     display: none;
 }
+
+::-webkit-scrollbar {
+    width: 8px;
+    background: rgba(0, 0, 0, 0.25);
+}
+
+::-webkit-scrollbar-button {
+    display: none;
+}
+
+::-webkit-scrollbar-track {
+    background-color: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+    background-color: rgba(255, 255, 255, 0.5);
+    border-radius: 5px;
+}