[apps.csv] Fill "main languages" column for every app
To make one thing clear first: This is about programming languages. For most projects hosted on an Gitlab instance or GitHub, this is easy to determine, as the project details reveal this information. For the existing entries the barrier of a language being mentioned is 10%, we also don't list items that are bound to the build system (e.g. cmake or meson), as that's a seperate column.