Merge branch 'KPM' into 'main'

lowdin/__init__.py

lowdin/block_diagonalization.py

lowdin/kpm_funcs.py

lowdin/linalg.py

lowdin/poly_kpm.py

lowdin/series.py

lowdin/tests/test_block_diagonalization.py

lowdin/tests/test_linalg.py

pyproject.toml