Send issues on iOS

Issues are useful to keep track of errors that do not cause a crash but you would like to hear about:

Bugfender.sendIssueReturningUrl(title: "Server returned an error", text: "Request to /service/1234 returned 500")

You can also send rich text with Markdown:

Bugfender.sendIssueReturningUrl(title: "Server returned an error", text: "Request to `/service/1234` returned **500**")