various fixes to the "miscellaneous usage notes" section

- change “miscellaneous usage notes” section from h5 heading to h3
heading in line with all the other sections on the page – at this point
it’s pretty in depth so it’s not really secondary to the “Instructions”
section
- add bullets back to miscellaneous notes section
- point to d3 classed() method in the documentation to explain how to
override the hard-coded class names added to the divs in the
foreignObjects.