add(ags/bar): network section + tweak styles

ags/lib/widgets/separator.tsx

@@ -0,0 +1,8 @@
+import { Gio } from "astal";
+
+export default function Separator() {
+    return <image
+        cssClasses={["separator"]}
+        gicon={Gio.Icon.new_for_string("switch-on-symbolic")}
+    />
+}