Although the language you want to use for search is not listed on the Supported Languages, please note that the engine itself is language agnostic, so you can still use your language in your index, but you will lose access to the language specific features such as ignorePlurals, removeStopWords, and CJK word-detection.
If you can't find the language you want to use for search in your index Configuration > Language settings, you can leave the language setting empty, or if there is another language similar to your langue, that might be more helpful - we would recommend trying it both ways and see which way works best for you. You may test your search with a sample set of data in your index.