docs(fieldgroup): storybook adjustments for invalid

- Include aria-invalid in Storybook markup
- Add invalid arg to existing stories because they were showing
  a combination of options that were against the guidelines (a neutral
  variant help text with an invalid icon; this should use the negative
  variant).

Author: jawinn

components/fieldgroup/stories/fieldgroup.stories.js

@@ -1,6 +1,6 @@
 // Import the component markup template
-import { Template } from "./template";
 import { default as Radio } from "@spectrum-css/radio/stories/radio.stories.js";
+import { Template } from "./template";
 
 export default {
 	title: "Components/Field group",
@@ -58,6 +58,7 @@ export default {
 export const Vertical = Template.bind({});
 Vertical.args = {
 	layout: "vertical",
+	isInvalid: true,
 	items: [
 		{
 			id: "1",
@@ -73,6 +74,7 @@ Vertical.args = {
 export const Horizontal = Template.bind({});
 Horizontal.args = {
 	layout: "horizontal",
+	isInvalid: true,
 	items: [
 		{
 			id: "1",

components/fieldgroup/stories/template.js

@@ -1,10 +1,11 @@
 import { html } from "lit";
 import { classMap } from "lit/directives/class-map.js";
+import { ifDefined } from "lit/directives/if-defined.js";
 import { repeat } from "lit/directives/repeat.js";
 
 import { Template as FieldLabel } from "@spectrum-css/fieldlabel/stories/template.js";
-import { Template as Radio } from "@spectrum-css/radio/stories/template.js";
 import { Template as HelpText } from "@spectrum-css/helptext/stories/template.js";
+import { Template as Radio } from "@spectrum-css/radio/stories/template.js";
 
 import "../index.css";
 
@@ -35,6 +36,7 @@ export const Template = ({
 				[`${rootClass}--${layout}`]: typeof layout !== "undefined",
 				...customClasses.reduce((a, c) => ({ ...a, [c]: true }), {}),
 			})}
+			aria-invalid=${ifDefined(isInvalid ? "true" : undefined)}
 		>
 			${FieldLabel({
 				...globals,