BREAKING CHANGE: on Ubuntu 20.04+, the `texlive-latex-extra` package is needed to generate the PDF output

You can now use the `--format=pdf` argument to save the data computed by
Kosmorro to a PDF file. The new `--output` argument must be given with
the export file path.

BREAKING CHANGE: invoking kosmorro command without --latitude and
--longitude arguments will now only output the Moon phase and,
eventually, the events for the given date (or today if date not given).

BREAKING CHANGE: invoking kosmorro command with the --altitude argument
will now fail with an "unrecognized arguments" error.