[feature request] filter challenges by language/framework

[fjneumann]

First of all thank you for the great work youre doing with this, solving the challenges is a lot of fun!
Currently in the challenges view, we can filter challenges by whether they are completed or not. It would be great if we could also filter them by which language/framework they have already been completed in.

[kunal-mansukhani]

@ishaan-arya