Added static type, improved code quality and fixed bugs
* Switched to pre-commit for code-formatting
* Updated github workflow
* Added pytest for CLI args
* Added HETATM keyword for PDB reader (https://github.com/charnley/rmsd/pull/89)
* Adding static types and type test (https://github.com/charnley/rmsd/pull/81)
* Fixed reorder inconsistency with print argument (https://github.com/charnley/rmsd/issues/93 https://github.com/charnley/rmsd/pull/94)