Add a button to copy markdown with playground information

Author: fee1-dead

ui/frontend/Output/Gist.tsx

@@ -57,13 +57,15 @@ const Links: React.SFC = () => {
   const gistUrl = useSelector((state: State) => state.output.gist.url);
   const permalink = useSelector(selectors.permalinkSelector);
   const urloUrl = useSelector(selectors.urloUrlSelector);
+  const markdownSnippet = useSelector(selectors.snippetSelector);
 
   return (
     <Fragment>
       <Copied href={permalink}>Permalink to the playground</Copied>
       <Copied href={gistUrl}>Direct link to the gist</Copied>
       <Copied href={codeUrl}>Embedded code in link</Copied>
       <NewWindow href={urloUrl}>Open a new thread in the Rust user forum</NewWindow>
+      <Copied href={markdownSnippet}>Markdown snippet with all the information</Copied>
     </Fragment>
   );
 };

ui/frontend/selectors/index.ts

@@ -194,7 +194,7 @@ const maybeOutput = (code: string, whenPresent: (_: string) => void) => {
   if (val.length !== 0) { whenPresent(code); }
 };
 
-const snippetSelector = createSelector(
+export const snippetSelector = createSelector(
   gistSelector, permalinkSelector,
   (gist, permalink) => {
     let snippet =