message: defaults: bind alt+f4 to closeWindow
diff: "keybindings":
  [
  { "command": "closePane", "keys": ["ctrl+shift+w"] },
  + { "command": "closeWindow", "keys": ["alt+f4"] },
  { "command": "copy", "keys": ["ctrl+shift+c"] },
  { "command": "duplicateTab", "keys": ["ctrl+shift+d"] },
  { "command": "newTab", "keys": ["ctrl+shift+t"] },
  