Add spelling check

[albtam]

I am trying to add a spelling check to the git hook.

Warning: this is a first shot which is not correctly working!

• Last line of the message commit is not checked
• If several words have a typo, only the first one is shown

@tommarshall Would you like to add the spelling check or you'd rather stick to initial post to write good commit. I don't have any shell experience and I didn't manage to make it work properly, any help would be welcomed ;)

I loosely took inspiration from this gist.