feat(pulls): show PR URL in detail view (#1036)

Fixes #1035.

## Summary
- include the pull request URL in `tea pr <number>` detail output
- keep `tea pr create` output to one URL by relying on the shared detail renderer
- add a focused regression test

## Tests
- `go test ./modules/print`
- `go test ./...`

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Leon Müller <mueller4leon@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/1036
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: LeonM <206012+leonm@noreply.gitea.com>
Co-committed-by: LeonM <206012+leonm@noreply.gitea.com>

modules/print/pull.go

@@ -73,6 +73,10 @@ func PullDetails(pr *gitea.PullRequest, reviews []*gitea.PullReview, ciStatus *g
 		out += "- Maintainers are allowed to edit\n"
 	}
 
+	if pr.HTMLURL != "" {
+		out = strings.TrimRight(out, "\n") + "\n\n" + pr.HTMLURL + "\n"
+	}
+
 	outputMarkdown(out, getRepoURL(pr.HTMLURL))
 }