[gitlab] Add templates for issues and MR

These template should be used when opening a new issue or merge

There are two templates under issue:
- Default.md which is a bug report
- suggestion.md which is for suggestion to be implemented

To use them, select the corresponding template in the dropdown
beside the title of the issue/merge request.

Only available once merge in the default branch.
3 jobs for gitlab_templates in 39 minutes and 4 seconds (queued for 4 seconds)