Add right padding to the Modal title

Apparently it would be possible by overriding the header inside the Modal component, @erouchet please give details whenever you're bored, so that not is-large modals would not look weird like this

changed milestone to %Arkindex 1.6.1

The button, which is handled by the Modal component for all modals, can have an ml-3 Bulma class to add some left margin to all modals. We "just" need to go through every modal of the frontend to check that we aren't messing with them

added P3 label

assigned to @mlbonhomme

mentioned in merge request !1690 (merged)

closed with merge request !1690 (merged)