Styles for the "steps" directive

Looks fine for steps that are less than 3 digits. We'll have to make some adjustments if we have steps that are greater than 99.

The other change I snuck in here is a revert for a mistaken commit I made that changes the letter-spacing in the docs, as well as the weird lack of margin in `mms.mongodb.org/help`'s sidebar that Sam and I discussed.