Add feature to pull crosswords from Guardian

[roygbyte]

Guardian has a number of crosswords available to the public. These could be included in the plugin as a "today's crossword" type of feature.

The structure of the JSON data is a bit different, unfortunately (also: inevitably). To have a peak at it, see this:
https://www.theguardian.com/crosswords/quick/16155 | sed -n 's/.data-crossword-data="([^"])".*/\1/p' | recode html..utf8