Initial packaging of usql

Closes: http://bugs.debian.org/1100934

This is a Merge Request targeting the branch debian/latest, which equals the upstream v0.19.19 tag contents and will get a debian/ subdirectory only starting from this MR being merged.

This MR will be updated/rebased until it is ready for upload.

Please share all the feedback you have. You don't need to be an expert in the domain - any feedback is valued. Also comments stating that you checked this out but didn't spot any issues are also valued, as it counts to the number of eyeballs that saw this before upload.

See also newgateway-team/reviews#10 (closed)