feat: add LaTeX and 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.

chore(deps): bump skyfield from 1.16 to 1.17

Bumps [skyfield](https://github.com/brandon-rhodes/python-skyfield) from 1.16 to 1.17.
- [Release notes](https://github.com/brandon-rhodes/python-skyfield/releases)
- [Changelog](https://github.com/skyfielders/python-skyfield/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/brandon-rhodes/python-skyfield/compare/1.16...1.17)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Unit tests are already run by the Code coverage step (renamed to Unit
tests)

Add colors in the text return

Colors can be disabled with the new `--no-colors` argument.

Make the strings translatable

chore(deps): bump numpy from 1.18.0 to 1.18.1

Bumps [numpy](https://github.com/numpy/numpy) from 1.18.0 to 1.18.1.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/master/doc/HOWTO_RELEASE.rst.txt)
- [Commits](https://github.com/numpy/numpy/compare/v1.18.0...v1.18.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Add support for conjunctions

chore(deps): bump numpy from 1.17.4 to 1.18.0

Bumps [numpy](https://github.com/numpy/numpy) from 1.17.4 to 1.18.0.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/master/doc/HOWTO_RELEASE.rst.txt)
- [Commits](https://github.com/numpy/numpy/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Python 3.8 is currently not available on Mac, making the installation
hard for development purpose

chore(deps): bump skyfield from 1.15 to 1.16

Bumps [skyfield](https://github.com/brandon-rhodes/python-skyfield) from 1.15 to 1.16.
- [Release notes](https://github.com/brandon-rhodes/python-skyfield/releases)
- [Changelog](https://github.com/skyfielders/python-skyfield/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/brandon-rhodes/python-skyfield/compare/1.15...1.16)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Rename fields in the JSON response for more coherence

BREAKING CHANGE: the fields "details" and "ephemerides" have been switched.

feat(ephemerides): compute ephemerides if the position is set only

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).

Add support for opposition events

fix(moonphase): fix the Moon phase prediction

instead of "Planet" in the text format output