Update level.sass to fix issue with icons (#1193)

Update level.sass to fix issue with icons (#1193)

* Update level.sass

Removing `margin-right: 0.75rem` from the `level is-mobile` in #1153 changed the spacing of icons used in the `level-items`. This pr restores the margin-right for the icon class only to restore the behavior as before while keeping changes made in #1153.

* Update level.sass

the margin for icons should be only for level is-mobile.

* Update level.sass

* add margin-right to level-item

* add margin to .level.is-mobile .level-item

made suggested changes