Ensure longer headers in table of contents spill more gracefully

[Soumaya Mauthoor (SoumayaMauthoorMOJ)]

#45 and #48 means that longer subheadings don't carry over nicely:

A temporary work-around is to use short titles. A better solution would be to make the titles spill over the next line? Or perhaps this is a good way of forcing people to use more succinct titles?