batches: document how to ignore templating delimiters

Created by: courier-new

Adds an FAQ + cheatsheet example of writing a batch spec and ignoring the GitHub expressions syntax used in a step, as well as some explanation of how to escape characters when necessary. Double-checked that the example spec runs correctly 😉 (thanks to Adam + Erik again for helping me work that out).

I also noticed + fixed two couple minor visual things:

1. When the right nav menu had enough entries, or the window was short enough, the bottom of the menu would get cut off:

   Before

   After

2. The page header # anchor that would appear on hover looked awfully mis-aligned with bigger headers:

   Before

   After