Solarmach

<!-- Release notes generated using configuration in .github/release.yml at v0.3.3 -->

What's Changed
* Bugfix: `get_sw_speed` has been fixed to work again for Solar Orbiter (due to some changed ID)
* Some internal changes in the pfsspy part

**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.3.2...v0.3.3

<!-- Release notes generated using configuration in .github/release.yml at v0.3.2 -->

What's Changed
* Bugfix: PFSS extension now gives correct results when Stonyhurst coordinates are used (`coord_sys='Stonyhurst'`). Now, when calculating the PFSS solution, it is necessary to define the coordinate system that should be used. For example, `calculate_pfss_solution(gong_map=gong_map, rss=rss, coord_sys='Stonyhurst')`

**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.3.1...v0.3.2

<!-- Release notes generated using configuration in .github/release.yml at v0.3.1 -->

What's Changed
* Add new option `markers` to the plot to use a single letter for the body/spacecraft marker instead of numbers (e.g., "P" for Parker Solar Probe). Note that duplicate letters can occour. This option replaces the previous plot option `numbered_markers`. For now on, use either `markers='letters'` or `markers='numbers'` (or `markers=False` for the default square symbol). See the following example:

python
from solarmach import SolarMACH
body_list = ['Venus', 'Earth', 'Mars', 'STEREO A', 'Solar Orbiter', 'PSP', 'BepiColombo']
date = '2021-6-1 12:00:00'
sm = SolarMACH(date, body_list)
sm.plot(markers='letters')


**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.3.0...v0.3.1

<!-- Release notes generated using configuration in .github/release.yml at v0.3.0 -->

What's Changed
* Discontinue support for Python 3.7 due to dependencies

Bugfixes 🛠
* Fix `get_sw_speed()` to work with updated AMDA system

**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.2.6...v0.3.0

<!-- Release notes generated using configuration in .github/release.yml at v0.2.6 -->

What's Changed
* Add new function `sc_distance()` ([see documentation](https://solarmach.readthedocs.io/en/latest/api/solarmach.sc_distance.html)) that derives the absolute distance between two bodies/spacecraft at a given time

Bugfixes 🛠
* Fix `test_solarmach_get_sw_speed()` for conda-forge


**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.2.5...v0.2.6

<!-- Release notes generated using configuration in .github/release.yml at v0.2.5 -->

What's Changed
* Create conda-forge version of `pfsspy`, and make loading of `speasy` optional, so that conda-forge version of `solarmach` can be updated (41)

Bugfixes 🛠
* Fix handling of `NaN` results in `get_sw_speed()`, defaulting to `default_vsw` in this case
* Fix some small bugs in PFSS extension
* Fix `plotly.graph_objs.Line is deprecated.`

**Full Changelog**: https://github.com/jgieseler/solarmach/compare/v0.2.4...v0.2.5