guicmds: mark additional translatable string

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
doc: add zh_TW version of hotkeys.html

All non fuzzy strings are translated.  The future addition of zh_TW
translation will point to hotkeys_zh_TW.html

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Merge pull request #265 from Vdragon/master

Improve zh_TW localization

Signed-off-by: David Aguilar <davvid@gmail.com>