Difficulty tweak - letters tracking

Big thanks to everyone who has streamed the game and helped us tune its difficulty!

This update adds the ability to fill in senders and recipients of letters sent between characters, and the quiz page will show when these are marked correctly. A few puzzles and wordings have been tweaked as well.

For posterity the original jam version (v2) is also available for download, which provides much less interim progress feedback (aka hard mode!).