symbols for certain keys
? == command
? == option
? == control
fn == function
? == shift
? == caps Lock
? == delete
? == 向前刪除鍵（fn?）
? == Return/Enter
↑ == 上箭頭
↓ == 下箭頭
← == 左箭頭
→ == 右箭頭
? == page up（fn↑）
? == page down（fn↓）
home == fn←
end == fn→
? == 右制表符（tab）
? == 左制表符（?tab）
? == escape (esc)
? == 電源開關鍵
??. 顯示隱藏文件
?H Hide the windows of the front app. To view the front app but hide all other apps, press ??H.
?W Close the front window. To close all windows of the app, press ??W.
參考資料：
http://www.reibang.com/p/735ba08df1fa
https://support.apple.com/en-us/HT201236
