Allow creating issues by sending a service desk email

[ghost91-]

This would be useful for situations where the repository is in a self hosted GitLab instance or even if there is no repository at all but the module developer provides an email address that bug reports can be sent to.

For example, I host a couple of my packages on a self hosted GitLab instance so currently, people cannot use bug reporter to report bugs there because it is not integrated. In order for people to be able to create issues without having an account, I've set up the help desk feature of GitLab, so that they can create issues simply by sending an email to a specific email address. It would be very nice if bug reporter would be able to send these emails.

The idea would be that an additional property bugEmail or similar is added to manifest+ and if this property is present and a valid email address, bug reporter sends an email to this address when a user submits a bug via bug reporter.