Add mystiq in backprts

[Pablo Mestre <mestre@lambdaforge.io>]

Hello,

I'm in charge of the packaging for mystiq [1] which is in the sid branch.
This package is a media converter thats can read audio and video files
in various formats and convert them into other formats. MystiQ features
an intuitive graphical interface and a rich set of presets to help you
convert media files within a few clicks. Advanced users can also adjust
conversion parameters in detail.

I want to introduce also on Buster but I still learning abpout
packaging. Whats are your opinions about it?

Pablo

[1] https://tracker.debian.org/pkg/mystiq