Merge branch 'main' into feature/3.0/barycentric_interpolation

.clang-format

.gitignore

.gitlab-ci.yml

CMakeLists.txt

NEWS.txt

QUICKSTART.md

README.md

ToDO.md

bench/fmm_generic.hpp

bench/loop_leaf.cpp

checks/CMakeLists.txt

checks/check_1d.cpp

checks/check_2d.cpp

checks/check_max_morton_level.cpp

checks/check_mpi.cpp

checks/count_particles_gen.hpp

checks/count_particles_mpi.cpp

checks/count_particles_omp.cpp

checks/count_particles_st_gen.hpp

checks/test_build_let.cpp