Add a web browser tab.

src/style.css

@@ -120,6 +120,50 @@
   opacity: 1;
 }
 
+.vtabs-pane-icon {
+  color: #6f6784;
+  -gtk-icon-size: 14px;
+}
+
+.vtabs-pane.active .vtabs-pane-icon {
+  color: #b29df5;
+}
+
+/* A web pane's navigation bar, below the pane header. Kept visually quieter
+   than the header so the two rows don't compete. */
+.vtabs-nav {
+  padding: 4px 6px;
+  background-color: #16141c;
+  border-bottom: 1px solid #262133;
+}
+
+.vtabs-nav-button {
+  min-width: 24px;
+  min-height: 24px;
+  padding: 0;
+  color: #b6afc7;
+}
+
+.vtabs-nav-button:disabled {
+  opacity: 0.3;
+}
+
+.vtabs-nav-entry {
+  min-height: 24px;
+  margin-left: 4px;
+  padding: 2px 8px;
+  border-radius: 6px;
+  font-size: 0.85em;
+  background-color: #0f0d14;
+  color: #ded7ef;
+  border: 1px solid #2a2536;
+  box-shadow: none;
+}
+
+.vtabs-nav-entry:focus-within {
+  border-color: #5b4d80;
+}
+
 /* The pane being dragged. There is no separate drop indicator: the layout
    rearranges live during the drag, so the view itself is the preview. */
 .vtabs-pane.dragging {