Add in-game chat

When connected to a server, there should be a chat box that players can use to communicate via text and that the server can use to send players messages (clients joining/leaving). This should be implemented similarly to Minecraft's chat. New messages should appear briefly before fading out, and the entire history can be brought up when entering mouse mode with left alt. There should be a keybind to start typing, along with being able to click on the textbox in mouse mode.