Ldrb

What's Changed
* Add code of conduct by finsberg in https://github.com/finsberg/ldrb/pull/94
* Add contributing guidelines by finsberg in https://github.com/finsberg/ldrb/pull/95
* Contributing guidelines by finsberg in https://github.com/finsberg/ldrb/pull/96
* Markers have optional list by Reidmen in https://github.com/finsberg/ldrb/pull/99

New Contributors
* Reidmen made their first contribution in https://github.com/finsberg/ldrb/pull/99

**Full Changelog**: https://github.com/finsberg/ldrb/compare/v2023.4.0...v2023.5.0

What's Changed
* Write strocchi demo in paralell by finsberg in https://github.com/finsberg/ldrb/pull/70
* Fix major bug in bislerp algorithm by jamtrott and finsberg in https://github.com/finsberg/ldrb/pull/72
- Add correct rotation matrix
- Swap order of products in bislerp algorithm similar to https://gitlab.com/lifex/lifex/-/blob/main/source/numerics/quaternions.cpp#L208


**Full Changelog**: https://github.com/finsberg/ldrb/compare/v2023.2.0...v2023.3.0

Use superlu as linear solver for Laplace equation