[Feature Request] Add "Custom languages" filter.

[Pablohn26]

First of all, thanks for your contribution. It is always nice to see open source apps on Play Store.

On Languages menu you can select all the languages that you are interested at. All filter shows all languages and then you can filter by language. Would be possible to add another filter that filter by all the languages (custom languages) that you have enabled?

Basic example: if you have only as language C and C++, you are be able to search filter by All languages (no filter), C or C++. I would like a filter to filter by C and C++ (and also All languages filter). I hope it is well explained.