Add Merge Request template

Hi, I propose to use a MR template within the project in order to make sure that we do not skip information that might be relevant when asking for reviews.

As it's a template, it can easily be modified or removed when not needed (case in point: I'm not using it now). We'd need to have it in master, then activate the option in the repo.

See: https://git.xfel.eu/gitlab/help/user/project/description_templates

It's a template I've used in other projects, or here , which I think exhaustive enough.

@ahmedk @kamile @amunnich @tmichela

.gitlab/merge_request_templates/default.md

@@ -14,16 +14,18 @@
 <!-- Include any relevant screenshot, elogs, reports, if appropriate. -->
 
 ## Types of changes
-<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
-- [ ] Bug fix (non-breaking change which fixes an issue)
-- [ ] New feature (non-breaking change which adds functionality)
-- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+<!--- What types of changes does your code introduce? Uncomment all lines that apply: -->
+
+<!-- - Bug fix (non-breaking change which fixes an issue) -->
+<!-- - New feature (non-breaking change which adds functionality) -->
+<!-- - Breaking change (fix or feature that would cause existing functionality to not work as expected) -->
 
 ## Checklist:
-<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
-- [ ] My code follows the code style of this project.
-- [ ] My change requires a change to the documentation.
-- [ ] I have updated the documentation accordingly.
+<!--- Go over all the following points, and uncomment all lines that apply: -->
+
+<!-- - My code follows the code style of this project. -->
+<!-- - My change requires a change to the documentation. -->
+<!-- - I have updated the documentation accordingly. -->
 
 ## Reviewers
 <!--- Tag a minimum of two reviewers -->