Make "Jump To Section" in docs more prominent

In the consul API documentation there is a "Jump To Section" pull down at the top of each section. For a long time I've wanted that feature but didn't notice it until today. I think it would be more helpful if made more prominent so it'd be easier to spot.

Start by reviewing the Consul API documentation sections and the existing “Jump To Section” pull-down at the top of each section. Determine how its visibility can be improved, then verify that the control is consistently easier to notice and remains usable throughout the documentation.

Written by the indexing model from the issue text.