deps: lock gogio version
feat: display current player name in header
bugfix: avoid crashing when laying out help
feat: reskin start screen
feat: change background to match battlefield
feat: switch to dark theme
feat: prevent off-turn button presses
feat: add click instructions during player turn
feat: click cards to play; remove play buttons
bugfix: ensure nonexistent cards cannot be played
bugfix: remove waitgroup race by adding before spawning goroutine
feat: ensure card names are visible in help menu
deps: switch to latest enter/leave gio fork
bugfix: defend from misbehaving websocket connection

Previously, a websocket connection with no pending messages could crash
the server.
deps: update to latest gio
doc: clarify project status
bugfix: eliminate index error when playing last card in hand
feat: remove noisy logging
feat: censor gamestate sent to each player
feat: prevent usernames from breaking layout