Add CLI

[JannisNe]

Add a CLI using typer. The dependencies will not be installed by default but are included as extras cli. So to run the CLI nuztf has to be installed via poetry install -E cli.

The command is nuztf and documentation is provided in the help message nuztf --help and the README.

[coveralls]

coverage: 73.615% (+0.6%) from 72.978%
when pulling 9758a83 on cli
into 5d4c681 on main.

[robertdstein]

Looks good. One request: can you either exclude this from coveralls calculations, or add a test?

[robertdstein]

Sorry, one more request: rather than a real tempfile can you use https://docs.python.org/3/library/tempfile.html ? Then even if the test is interrupted the file gets cleaned up. You can use it within a with statement.

[JannisNe]

I actually started using the tempfile package. However, I found it then useful if the test gcn is still there if the test fails to check what exactly changed.

[robertdstein]

Makes sense!