Show issue reactions (#421)

```
$ tea issue 230

   #230 issue/pull details: show reactions (open)

  @6543 created 2020-10-22 16:39

  since reactions are utf8 now and most terminals too, we can display them nicely :)

  https://gitea.com/api/v1/repos/gitea/tea/issues/230/reactions

  --------

  1x 🎉  |  1x 👀  |  1x   |  1x 👍  |  1x 👎  |  1x 😆  |  1x 😕  |  1x ❤️
```

caveats:
- reactions are not returned as UTF8 (as was claimed in #230), so they need to be parsed. the library I use doesn't (and can't → ) support all reactions available in gitea
- currently only for issues, as reactions for comments mean an additional API request for each comment..

fixes #230

Co-authored-by: Norwin <git@nroo.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/421
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Norwin <noerw@noreply.gitea.io>
Co-committed-by: Norwin <noerw@noreply.gitea.io>

cmd/issues.go

@@ -54,11 +54,16 @@ func runIssueDetail(cmd *cli.Context, index string) error {
 	if err != nil {
 		return err
 	}
-	issue, _, err := ctx.Login.Client().GetIssue(ctx.Owner, ctx.Repo, idx)
+	client := ctx.Login.Client()
+	issue, _, err := client.GetIssue(ctx.Owner, ctx.Repo, idx)
 	if err != nil {
 		return err
 	}
-	print.IssueDetails(issue)
+	reactions, _, err := client.GetIssueReactions(ctx.Owner, ctx.Repo, idx)
+	if err != nil {
+		return err
+	}
+	print.IssueDetails(issue, reactions)
 
 	if issue.Comments > 0 {
 		err = interact.ShowCommentsMaybeInteractive(ctx, idx, issue.Comments)