task list: visually separate "new task" row from others
The "new task" row doesn't stand out visually from the other list items. Increasing the margin-top on GtdNewTaskRow a bit would improve this by separating it from the existing rows.
Current (margin-top: 3):
Proposed (margin-top: 12):
- Define new margins
- Increase margin to 12 when there are tasks in the list, but not when the list is empty
- Margin is 12 when there are tasks in the list, and the same as before when it's empty
- No regressions were introduced