Ffsim

- changes spin order of `indices_to_strings` to (beta, alpha) instead of (alpha, beta), so that little endianness is consistent.

**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.20...v0.0.21

What's Changed
* switch givens rotation orbital rotation to slower python code to work around bug by kevinsung in https://github.com/qiskit-community/ffsim/pull/96


**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.19...v0.0.20

What's Changed
* add support for acting on just one spin sector by kevinsung in https://github.com/qiskit-community/ffsim/pull/91


**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.18...v0.0.19

What's Changed
* add on-site number-number interaction gate by kevinsung in https://github.com/qiskit-community/ffsim/pull/86
* Return lower ranks of RDMs by kevinsung in https://github.com/qiskit-community/ffsim/pull/88
* Add linear method for optimization of variational wavefunction by kevinsung in https://github.com/qiskit-community/ffsim/pull/89


**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.17...v0.0.18

What's Changed
* Add final orbital rotation to hop gate ansatz by kevinsung in https://github.com/qiskit-community/ffsim/pull/85

Breaking Changes
* Parameter ordering of UCJAnsatz has changed. See 85 .

**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.16...v0.0.17

What's Changed
* add real-valued ucj operator by kevinsung in https://github.com/qiskit-community/ffsim/pull/77
* add functions and tests for random two-body tensors by kevinsung in https://github.com/qiskit-community/ffsim/pull/79
* add orbital rotation for molecular hamiltonian by kevinsung in https://github.com/qiskit-community/ffsim/pull/80


**Full Changelog**: https://github.com/qiskit-community/ffsim/compare/v0.0.15...v0.0.16