Update es-ES.coffee

Line #231, “Atajos de teclado” means “Keyboard Shortcuts” — let me know if this isn’t close enough to what is meant by “Key Bindings”: the reason that I chose this phrase is because I don’t know of an exact or approximate translation of “key bindings” into Spanish, but several other software platforms have used the phrase “atajos de teclado” to express this meaning.