Update issue template

Github has started using a new issue templating structure.
This commit moves the current template and adds one additional one.

• Moves issue template to new issue-template folder
• Adds feature request template
• removes the following warning when viewing issue template

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Kjeld Schouten-Lebbing <kjeld@schouten-lebbing.nl>
Closes #10759