suppress email notifications on New Issue

[cloudcon]

The checkbox to suppress notifications by e-mail, would also appear to register a new issue.
Often we can solve a problem via chat or another email or even through a personal order so I believe that when creating this issue who delegated the task would not need to receive an email notifying that it was registered

[tofi86]

While displaying the checkbox below the form field can easy be achieved with adding

    render_on :view_issues_form_details_bottom,
      :partial => 'hooks/silencer_suppress_mail'

below https://github.com/paginagmbh/redmine_silencer/blob/master/lib/redmine_silencer/view_hooks.rb#L6-L7

1. the checkbox is being showed twice when editing an existing issue
2. the changed checkbox state is being reset when a form field changes and triggers a form reload (e.g. status change)

Unfortunately, I do not have a solution to any of the two problems.

Contributions are welcome! 🥇