[RFC] Add IRC pane 

Resolves #2.
In the old code, the size of the DF window streched to fit the size of the controlling player's screen. Since part of that screen is now covered with a chat window, that had to get fixed somehow. To make this PR work I did the dumbest thing that could possibly work, which is hardcode the size to the default and scale the canvas size afterward to fit the window width. This is probably not ideal, but it's a step in the right direction  IMO because previously, no scaling was done at all, and screens could grow to server-crashing sizes (see https://archive.moe/vg/thread/83566642/#83576774)