aburrell/aacgmv2: Version 2.6.3

A bug-fix release that fixes a memory leak in aacgmv2.convert_latlon_arr and the output format for longitude in aacgmv2.convert_mlt. Other maintenance issues were addressed, including adding a pyproject.toml, improving the unit test standards, extending the documentation, and moving CI to GitHub Actions.When referencing this package, please cite both the package DOI and the AACGM-v2 journal article: Shepherd, S. G. (2014), Altitude‐adjusted corrected geomagnetic coordinates: Definition and functional approximations, Journal of Geophysical Research: Space Physics, 119, 7501–7521, doi:10.1002/2014JA020264