Enhance OuiLink documentation (#1182)

Signed-off-by: Willie Hung <[email protected]>

src-docs/src/views/link/link.js

@@ -11,7 +11,7 @@
 
 import React from 'react';
 
-import { OuiCode, OuiLink, OuiText } from '../../../../src/components';
+import { OuiCode, OuiLink, OuiText, OuiIcon } from '../../../../src/components';
 
 export default () => (
  <OuiText>
@@ -28,7 +28,9 @@ export default () => (
  <OuiLink href="https://oui.opensearch.org/latest/" external>
  link
  </OuiLink>{' '}
- has the <OuiCode>external</OuiCode> prop set to true.
+ has the <OuiCode>external</OuiCode> prop set to true. A pop-out icon{' '}
+ <OuiIcon type="popout" size="s" /> will be automatically rendered to
+ indicate that it leads to an external resource.
  </p>
  <p>
  This link is actually a <OuiLink onClick={() => {}}>button</OuiLink> with