Bug 48332: Serialize new category links on their own line

We are assuming that new category links are only added at the end of the
document, so we don't have to worry about them being added in the middle of
list items or other line-based syntax.

Bug: 48332
Change-Id: I7c24f83e59677c0c7ec979c1dedec2d44c1ec7c4
Merge "Bug 48332: Serialize new category links on their own line"