Consider different favicons for puzzle list page and puzzle pages

[jpd236]

Passing along a feature request from a member of my team for tracking, though I don't currently plan to get to this myself:

Currently all JR pages use the same favicon. If you have many tabs (and thus only a little room, if any, to see page titles), one of which is the main puzzle list page, with others for various puzzles, it can be hard at a glance to see which tab is the list page vs. the individual puzzles. They suggested using a different favicon/badging to differentiate these two and make it easier to go back to the list.