Caribou strings

[Claude Paroz <claude 2xlibre net>]

Hi,

I just fixed typos in two Caribou strings. [1]
I also added translator comments for keyboard types (Touch/Full
scale/Scan), thanks to Eitan Isaacson explanations. I think that it
would be worth checking the validity of existing translations for these
strings.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=658053

Claude
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