add test and docs

Author: broccolinisoup

packages/react/src/Dialog/Dialog.docs.json

@@ -59,6 +59,11 @@
       "name": "returnFocusRef",
       "type": "React.RefObject<HTMLElement>",
       "describedby": "Return focus to this element when the Dialog closes, instead of the element that had focus immediately before the Dialog opened"
+    },
+    {
+      "name": "initialFocusRef",
+      "type": "React.RefObject<HTMLElement>",
+      "description": "Focus this element when the Dialog opens"
     }
   ],
   "subcomponents": []

packages/react/src/Dialog/Dialog.test.tsx

@@ -209,3 +209,21 @@ describe('Dialog', () => {
     expect(getByRole('button', {name: 'return focus to (button 2)'})).toHaveFocus()
   })
 })
+
+it('automatically focuses the element that is specified as initialFocusRef', () => {
+  const initialFocusRef = React.createRef<HTMLAnchorElement>()
+  const {getByRole} = render(
+    <Dialog
+      initialFocusRef={initialFocusRef}
+      onClose={() => {}}
+      title="New issue"
+      renderBody={() => (
+        <a ref={initialFocusRef} href="https://github.com">
+          Item 1
+        </a>
+      )}
+    ></Dialog>,
+  )
+
+  expect(getByRole('link')).toHaveFocus()
+})