Add Fieldset component for structured grouping

src/components/Fieldset.js

@@ -0,0 +1,19 @@
+import { $html } from "sigpro";
+import { val, joinClass } from "../core/utils.js";
+
+/** FIELDSET */
+export const Fieldset = (props, children) =>
+  $html(
+    "fieldset",
+    {
+      ...props,
+      class: joinClass("fieldset bg-base-200 border border-base-300 p-4 rounded-lg", props.class),
+    },
+    [
+      () => {
+        const legendText = val(props.legend);
+        return legendText ? $html("legend", { class: "fieldset-legend font-bold" }, [legendText]) : null;
+      },
+      children,
+    ],
+  );