Add apt_add to add deb repository

See merge request xebis/shellib!24

# [0.11.0](https://gitlab.com/xebis/shellib/compare/v0.10.0...v0.11.0) (2022-01-07)

### Features

* add apt_add to add deb repository ([f4b22f09](https://gitlab.com/xebis/shellib/commit/f4b22f09f5b6412180f2556a5a5101c3ef056ffc))