feat(downstate): docs + implementation for example components (#2520)

* feat(downstate): docs + implementation for example components

* docs: update mdx

* docs: reorg, stories live within foundations

* docs: decorator for down state dimension tokens

* docs: fix mdx hierarchy console error

* fix: small iconOnly button gets min perspective

* docs: use markdown, update language

* fix: disabled, readonly checkbox doesnt have down state

* chore(button,checkbox): update package versions

.storybook/foundations/down-state/button-down-state.stories.js

@@ -1,4 +1,4 @@
-import { Template } from "../../../components/button/stories/template";
+import { Template } from "@spectrum-css/button/stories/template";
 
 export default {
 	title: "Foundations/Down state",

.storybook/foundations/down-state/checkbox-down-state.stories.js

@@ -1,4 +1,4 @@
-import { Template } from "../../../components/checkbox/stories/template";
+import { Template } from "@spectrum-css/checkbox/stories/template";
 
 export default {
 	title: "Foundations/Down state",
@@ -10,10 +10,10 @@ export default {
 	},
 	parameters: {
 		actions: {
-			handles: ["click input[type=\"checkbox\"]"],
+			handles: ['click input[type="checkbox"]'],
 		},
 	},
-	tags: ["foundation"],
+	tags: ['foundation'],
 };
 
 export const CheckboxDownState = Template.bind({});