[Feature Request] Add Czech support

[vggscqq]

First of all thank you a lot for the extension. Been using it for a very long time to extend my vocabulary.
Since I started to learn Czech language I started to struggle trying to google all the words I read. If it's possible it would be nice to get Czech as an additional language to use.
As far as I understood the code it's not possible(I don't know JS), cause google isn't show the definition for words in Czech. i.e. it won't show it by searching for define ahoj or definice ahoj [define hi and definition hi] queries.

Thanks in advance.