A few CSS overrides to make the documentation useful on small screens, such as phones

[stuartlangridge]

The woven Inform7 docs aren't all that useful on a small screen like a phone, because the layout rather assumes that the screen is wide and so can happily have two columns, with the navigation menu on the left. This is a very (very) basic set of overrides for narrower screens, which put the nav menu at the end (rather than on top of the main content) and so make the docs readable fine on a phone. There are doubtless other problems here (in particular, ASCII art diagrams and tables and the like are decidedly imperfect still) but these small tweaks are probably a material improvement on small screens over what's there currently, even if they don't solve everything.